dynamic heart

The essays in this book are inspired by a Goethean view of the organism

and of science. They are an attempt to “portray rather than explain.” Some

essays give precise descriptions of physiological processes, while others

portray the heart and circulation within broader developmental and

evolutionary contexts. The intricacies of the circulatory system and its

place within the whole human being come into view.

Written by doctors, scientists and teachers, the contributions in this

book present a dynamic picture of the circulatory system that both

balances and puts into perspective the prevailing one-sided mechanical

explanations that dominate science and medical education. High school

and medical students today do not usually learn “the heart has functions

that can be interpreted in terms of a pres sure pump”; rather, they learn

“the heart is a pump,” meaning that’s all it is. When a metaphor is taken

as a fact and becomes the sole lens through which one looks, the rich-

ness of reality recedes behind the sharp and narrow focus. One aim of

this book is to transcend this narrow view and to begin to restore life

to our under standing of the heart and circulation.

This book will fill a long-existing void in the literature. It will stimulate

teach ers, health professionals, scientists and lay people seeking a dynamic

perspective on human physiology that is both detailed and comprehensive.

Published byThe Association of Waldorf Schools of North America 38 Main Street

Chatham, New York 12037

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The Hea r t : A P u l s i ng an d P e r c ep t i v e C e nt e r 1

1

T h e H e a r t : A P u l s i n g a n d P e r c e p t i v e C e n t e r

C R A I G H O L D R E G E

We and Our Bodies: The Problem of Physiology

IN MY TWENTY YEARS as a high school biology teacher, I was always mostapprehensive about teaching human physiology. Not because the sub-ject might bore the students. And not because I knew I didn’t knowenough—that was a problem in all subjects. What worried me was aquestion that continually gnawed at me during preparation: Am Iteaching the students about reality, or about “facts” colored and dis-torted by models, theories, and prevailing habits of thought?

One problem with physiology is that it rarely deals with direct phe-nomena. Who can observe the blood flowing through the blood ves-sels? Who can observe the liver making bile and secreting it into thegall bladder? Most of the “facts” of physiology are in reality conclusionsbased on experimental or indirect evidence. Today science and medi-cine make use of sophisticated imaging techniques such as CAT scansand the MRIs. But these images too must be interpreted—they are notthe phenomena themselves. Moreover, human physiology textbooks

2 T H E D Y N A M I C H E A R T A N D C I R C U L A T I O N

are full of descriptions based on observations made in animal experi-ments. But do they apply to human beings?

Another difficulty—which I primarily want to address here – con-cerns physiology’s narrow scope. When we discuss the workings ofinternal organs as if they just happen, removed from their living con-text within us as sentient, thinking and active human beings, thenwe’re dealing with a phantom. To put it drastically: to teach physiologyby itself is to teach a lie. Over the years I struggled with this problem—and you can now see why I wasn’t overly eager to jump into the class-room, although the heart, the lungs, the liver, and the brain fascinatedme. But I didn’t want to teach about them as isolated things. I didn’twant to teach about them as mechanisms.

So I asked my students, by way of introducing a course in humanbiology, “What do we need to take into consideration if we are inter-ested in a comprehensive scientific understanding of the humanbeing? What might a true science of the human being encompass?”Since this was a biology course, it was natural to think first of the body.We should know anatomy—how the body is membered into parts andhow these parts are structured, connected, and ordered within thebody. Anatomy (which literally means “to cut”) involves dissection andis best done on corpses. It means taking apart the body, finding struc-ture within structure. Anatomy brings clarity and order, but it lacks life.What do we need to understand life? At a minimum we need to under-stand how organs grow, develop, and function and how all these func-tions are interrelated. We need the sciences of physiology,developmental biology, and ecology, to mention a few.

This is already a tall order, but even if we could describe all theseprocesses and functions, would we then have understood the humanbeing? Is that all that belongs to and determines us? High school stu-dents, at least, have a clear answer to this question: No! The sadness aboy feels after being dropped by his girlfriend is not physiology(although it expresses itself in body). Feelings are not to be found inthe organs. It soon becomes clear that much of what is most essentialand closest to us—our thoughts, feelings and hopes—is not directlysense perceptible. We all have inwardness, an interior, a soul—what-ever term we choose as a label—which is a very real and important partof the human being, even if it is not physically tangible.


Any thorough study of the human being must take this inner worldinto account. Simply put, we need a science of psychology. We can doa phenomenological study of the soul through introspection andthrough relating experiences with other individuals. But we can alsostudy, say, how emotions affect blood pressure or intestinal function,or how the latter affect emotions. Every student is crystal clear aboutthe fact that you can’t understand blushing merely as a dilation ofsuperficial blood vessels in the facial skin. You have to take intoaccount the person who was embarrassed. Without the feeling ofembarrassment there would be no change in physiology in the face. Amiraculous and mysterious connection. We’ve arrived at the mind-body problem, which has perplexed but also stimulated the humanmind for centuries. Framed in more modern terms, we’re dealingwith psychosomatics—the relations and interactions between the souland the body. Or to put it less dualistically, how our interior and exte-rior are different aspects of our being.

But is this enough? Imagine a doctor who treats you for an illness.He might have a good foundation in anatomy, physiology, psychoso-matics, and psychology, but still not treat you well. Why not? Becausehe didn’t see you as an individual, as a unique person. Every patient iskeenly aware of being treated by a physician as an instance of a dis-ease. I remember being treated by an ophthalmologist and thinkingafter the visit: “He would have liked it much better if I could have senthim my eyeball all by itself. The rest of me, it seemed, was just gettingin the way.” Every illness, for all its generality, has an individualdimension. It occurs at a particular time of life under particular innerand outer conditions. The illness also presents a task for the individ-ual. Evidently we need a science of the individual, an approachtoward the human being that allows us to recognize and understandhow the myriad features of being human live differently and uniquelyin each of us.

Against this background it is not hard to see how I came to theview that teaching physiology by itself, especially within the narrowframework of modern textbooks and college instruction, fosters notonly an inadequate but also false picture of the human being and ourhuman bodies. Of course we cannot address all the layers of thehuman being when we discuss a given organ. But we can recognize


that this multilayered understanding is, in the end, our goal and thatevery step we take is part of a work in progress.

A Goethean Approach

Few people know that Goethe coined the term morphology [20, p.216]. He used the word in short essays he wrote at the end of the 18th

century that were first published in 1817 [4, pp. 57-69]. He was not justinterested in introducing a new term for already extant work. Rather,he envisioned a new focus within biology. Morphology was for him nota new content, but a new way of looking. Here’s how Goethe describesmorphology:

Morphology may be said to include the principles of structured form and the formation and transformation of organic bodies…. The Germans have a word for the complex of existence presented by the physical organism: Gestalt [structured form]. With this expression they exclude what is changeable and assume that an interrelated whole is identified, defined, and fixed in character.

But if we look at all these Gestalten, especially the organic ones, we will discover that nothing in them is permanent, nothing at rest or defined—everything is in a flux of continual motion. This is why German frequently and fittingly makes use of the word Bildung [for-mation] to describe the end product and what is in process of pro-duction as well.

Thus in setting forth a morphology we should not speak of Gestalt, or if we use the term we should at least do so only in refer-ence to the idea, the concept, or to an empirical element held fast for a mere moment of time.

When something has acquired a form, it metamorphoses imme-diately into a new one. If we wish to arrive at some living perception of nature we ourselves must remain as quick and flexible as nature and follow the example she gives. (4, p. 57 and pp. 63-64).

Morphology uses the information provided by anatomy, chemistryand other relevant sciences. But it uses scientific data “to portray ratherthan explain” (4, p. 57). Goethe strove for a living understanding of


the organism that brought the dynamic wholeness of the organism tolight; he was not interested in explaining it through scientific models,which have the remarkable characteristic of taking life out of what theyrepresent.

Since morphology, in Goethe’s sense, deals with how organic struc-tures form and transform, it clearly leads into physiology. But just asGoethe went beyond the confines of anatomy in envisioning morphol-ogy, so also does he go beyond what we today call physiology:

The existence of organic nature is possible only insofar as organ-isms have structure, and these organisms can be structured and maintained as active entities solely through the condition we call “life.” Thus it was natural that a science of physiology should be established in an attempt to discover the laws an organism is des-tined to follow as a living being….

In thinking of an organism as a whole, or ourselves as a whole, we will shortly find two points of view thrust upon us. At times we will view man as a being grasped by our physical senses, and at times as a being recognized only through an inner sense or understood only through the effects he produces.

Thus physiology falls into two parts which are not easily sepa-rated, i.e., into a physical part and a spiritual part. In reality these are inseparable, but the researcher in this field may start out from one side or the other and thus lend the greater weight to one or the other. (4, p. 59)

The essays in this book are inspired by this Goethean view of theorganism and of science. They are an attempt to “portray rather thanexplain.” Some essays give precise descriptions of physiological pro-cesses, while others portray the heart and circulation within broaderdevelopmental and evolutionary contexts. In this way we can at leastbegin to intimate the intricacies of the circulatory system and begin tosee its place within the whole human being.

A Goethean approach to organisms, and especially to human physi-ology, still stands at a beginning. The contributions in this book are aneffort to present the fruitfulness of this approach in respect to the mor-phology and physiology of the human heart and circulatory system.


But they are only a beginning. I say this not to detract from the years ofwork that these efforts represent, but to emphasize how much morework is needed. For example, these essays just begin to enter the realmof what Goethe called spiritual physiology, and the areas of psychologyand the individual that I discussed above. Hopefully, they can providestimulus for further work in these fields. If you as a reader come awayfeeling that you have gained a more living portrayal of the heart andcirculatory system that enkindles your desire to understand moredeeply, then we’ll know the book was worth writing.

But getting this far means overcoming a substantial hurdle, namelythe limitations of the mechanical way we’ve come to view life over thepast centuries.

Mechanical Metaphors

Mechanical metaphors present one of the greatest hindrances tounderstanding human physiology—the liver is a chemical factory, thekidney is a waste treatment plant, the heart is a pump and the brain isa computer. Especially the last two metaphors conjure up the image ofa central causative power or command center from which all activityissues. It is the mechanomorphic mind that interprets the phenomenain light of metaphors that are easily accessible and understandable toit. We need to be clear that it is our mind that determines how we lookat the phenomena. If we lived in a poetic and not a technological age,the metaphor “the heart is a rose” might be felt to be much more pow-erful and adequate to the phenomena. A mind at home in themechanical world of cause and effect can hardly avoid seeing the heartas a pump circulating the blood through the body. We can interpret allsorts of data in terms of this model and even create astounding devicessuch as the artificial heart. But that doesn’t mean that, by itself, thismodel is adequate.

The strange thing about mechanical models is that they tend to beexclusive and occupy the mind at the expense of other metaphors orways of viewing. A high school or college student doesn’t usually learn“the heart has functions that can be interpreted in terms of a pressurepump,” rather they learn “the heart is a pump,” meaning that’s all it is.That’s what often happens to mechanomorphic metaphors in science.


They become fixed and literal, losing their vibrancy and openness asmetaphors that suggest relations. This makes them easier and clearerto apply. Unfortunately, it also moves them away from life.

Once such metaphors have become fixed in the mind, it can thenbe difficult to loosen these images so that something of the richness ofreality reenters the mind. One aim of this book is to contribute to thisloosening, to look at the heart and circulation in broader and moredynamic terms.

The Fluid Heart

One of the most striking features of the circulatory system is itsdynamism. While the brain rests firmly and still in its protective cas-ings, rhythmic movement, transformation, and the ability to mediateextremes characterize the circulatory system.

The anatomy of the heart alone shows that it is a dynamic organ.Most of the heart consists of muscle fibers (myocardium). These fibersare joined in bands that “present an exceedingly intricate interlace-ment” (5, p. 468). What may at first appear to be more or less distinctlayers of lengthwise (longitudinal), diagonal (transverse), and hori-zontal (ring) musculature are in reality connected bands of complexspiraling fibers.

The nineteenth-century English anatomist J. Bell Pettrigrew discov-ered the spiraling course of muscle fibers [described in 18]. He spokeof untying the Gordian knot of anatomy. In order to understand the“unusual and perplexing” arrangement of the fibers, Pettigrew had tocarefully separate the different layers of fiber from each other. Sincemuscle tissue does not easily separate, he had to boil the heart for sixhours and then leave it in alcohol for two weeks. Only then could heeasily separate the different layers. He discovered in the ventriclesseven layers—three outer, three inner and a middle layer.

Through careful dissection he discovered that the layers of musclefibers were interconnected. In other words, the layers of fibers werenot like layers of onion skin, but rather continuous sheets of spiralingfibers. 20th Century German anatomists Benninghof and Goerttler car-ried Pettrigrew’s investigations further. I will follow their description([1]; see figures 1 and 2).


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The outer muscle fibers begin at the upper part of the heart(called the base in medical terminology) and sweep down in counter-clockwise curves to the tip (apex) of the heart. There they looparound and form the so-called heart vortex (vortex cordis, see Figure 1,middle drawing). Those fibers that begin at the front (ventral side) ofthe heart enter the heart vortex at the back (dorsal side) of the heart

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while those that begin at the back sweep around to the front. Theseouter fibers loop around each other, creating the vortex pattern, andthen continue into the inside of the muscular wall and spiral backupward. Some of these fibers radiate in the papillary muscles thatmove the atrio-ventricular valves.

Fibers that lie deeper at the top of the ventricles spiral down—incontrast to the superficial fibers—clockwise. These fibers coil in moretightly and form nearly horizontal loops around the body of the ventri-cles before they sweep upward again to the top of the heart.

The best way to form a picture of this complex fiber arrangement isto study figure 2 and then try to recreate the spiraling with your hands.With repeated effort you begin to get a sense of the heart’s dynamicstructure, which Pettrigrew described as “exceedingly simple in princi-ple but wonderfully complicated in detail” [18, p. 514].

Since a muscle like the heart retains its form, we generally think ofit as being solid. Of course we know that it can change its shape, butwhen we realize that muscle consists of about 75% water, we begin tothink of it in more fluid terms. The spiraling and looping pattern ofthe heart fibers, including the beautiful heart vortex, is an image offluid movement. Pettigrew made casts of the heartcavities. Figure 3 shows the cast of the left ventricle ofa deer. One can see spiraling forms here as well. Theridges in the cast represent grooves in the actual cav-ity. These grooves are separated by the bands of papil-lary muscles that move the atrio-ventricular valves. AsPettrigrew writes,

The importance of these grooves physiologically cannot be over-estimated, for I find that in them the blood is moulded into three spiral columns… The spiral action of the mitral valve and the spiral motion communicated to the blood when pro-jected from the heart, are due to the spiral arrangement of the musculi papillares [papil-lary muscles] and fibres composing the ventri-cle, as well as to the spiral shape of the ventricular cavity. [18, p. 510]

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1 0 T H E D Y N A M I C H E A R T A N D C I R C U L A T I O N

The blood streaming through the heart also creates loops and vorti-ces. Like the fibers of the heart this movement is very complex andintricate. In a sense, what the blood does as a fluid has become formedin the muscular structure of the heart.

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To build up a living picture of the blood flow through the heart wehave to recognize that the direction of blood flow is radically altered bythe heart. Venous blood enters the right side of the heart through thesuperior and inferior caval veins, which are vertically oriented (see Fig-ures 4 and 5; see also Appendix A). From the right atrium the bloodstreams down into the right ventricle and then back upward into thepulmonary artery, which immediately branches horizontally to the rightand left to enter the lungs. In contrast, the blood that enters the leftside of the heart comes horizontally from the pulmonary veins. Fromthe left atrium it flows downward into the left ventricle and loopsupward into the ascending aorta. At the aortic arch three arteries(innominate, left subclavian, and left common carotid) ascend intothe head and arms, while the vertically descending aorta serves the restof the body. Thus the right side of the heart brings vertically flowing

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T he H ea r t : A P u l s in g a n d P e r c ep t i v e C en t e r 1 1

blood into the horizontal and the left side of the heart brings horizon-tally flowing blood into the vertical. This change in orientation is clearlyevident in the drawing of the cross that is formed by the caval veins andthe pulmonary veins (Figure 5).

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Recently, with the help of sophisticated imaging techniques, PhilipKilner and his colleagues have provided a more concrete idea of howthe blood streams through the heart itself [9, 10]. Blood flows into theatria when the atrio-ventricular valves are closed and the ventricle mus-cles contract (systole). The streams of blood entering the right atriumfrom the superior and inferior caval veins do not collide, but turn for-ward and rotate clockwise forming a vortex. The blood streaming intothe left atrium also forms a vortex, but it turns counterclockwise—another contrast between the right and left sides of the heart. (Toimagine this hold your index fingers close together, pointing down-ward in front of your chest; rotate the right index finger clockwise andthe left finger counterclockwise.)

When the atrio-ventricular valves open, the blood streams into therelaxed ventricles (diastole), again rotating, forming vortices that

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redirect the flow of blood. For a short moment the blood does notflow further and then the semilunar valves (which separate the ventri-cles from the outgoing arteries) open and the blood streams into thepulmonary artery and the aorta.

We’ve arrived at a picture of the intricate streaming, turning, loop-ing blood flow through the heart that follows a different pattern ineach of the four chambers. The coiling, looping heart fibers createcontractions that mirror and facilitate this dynamic coursing of theblood. The heart muscle does not work, as we often imagine it does,opening and closing as we can do with our fist, first forming a fist (sys-tole) and then relaxing the fist (diasole). Rather, the heartbeat (car-diac cycle) includes a much more complex array of movements.During systole the heart moves downward and oscillates slightly to thesides and also rotates around its own axis [8, p. 360 ff.; 13,14]. Duringdiastole it moves upward and rotates back in the opposite direction.Only the heart’s interwoven spiraling muscle fibers can produce thiskind of complex motion.

We see that blood flow, the form of the heart and the pattern of itsfibers, and the heartbeat are intimately entwined. We can’t think of onewithout the others. When we go back to the origin of the blood and theheart in embryonic development, it is no simple matter to say whatcame first (see Brettschneider’s preface to Woernle’s chapter in thisbook). Maybe it’s also just our mechanical way of thinking that wants tosee a clearly directional cause and effect relation between the heart andthe blood instead of a more living relation of mutual dependency.

This mutuality shows itself during the embryonic development ofthe heart. Early in its development the heart begins to form loops thatredirect blood flow. But before the heart has developed walls (septa)separating the four chambers from each other, the blood already flowsin two distinct “currents” through the heart [1]. The blood flowingthrough the right and left sides of the heart do not mix, but streamand loop by each other, just as two currents in a body of water. In the“still water zone” between the two currents, the septum dividing thetwo chambers forms. Thus the movement of the blood gives theparameters for the inner differentiation of the heart, just as the loop-ing heart redirects the flow of blood. Blood movement and heart dif-ferentiation belong together.


Pulsing Interplay

From the above considerations we can see how the heart is the cen-ter of the circulatory system. It connects the upper and lower parts ofthe body as well as, through the pulmonary circulation, the outer (air)with the inner.

We cannot understand the heart’s activity unless we consider theblood, peripheral circulation, and the metabolic activity of the otherorgans. A rapidly beating heart only brings more blood into the arte-rial system if it is receiving more blood from the veins, which in turn isdependent on the metabolic activity of the organs and muscles [seeLauboeck’s essay in this book]. The heart is continually adapting itsactivity to the needs and state of the body and person as a whole.

In strenuous activity, for example, we need more blood flowing tothe muscles, which are using greater amounts of oxygen. To accom-modate this need, the heart expands more in the diastolic phase(when it receives blood) and also increases its beating rate, whichtogether allow more blood to pass through the heart and into thelungs and muscles. But the heart is not simply pushing this blood intothe body. The lungs take in up to three times the amount of oxygenduring exercise, not only because of the increased diffusing capacityof oxygen, but because both lung alveoli (where diffusion occurs) andthe lung capillaries dilate, letting more blood pass through the lungs[6, p. 481ff.]. Similarly, in the muscles the blood vessels actively dilate,allowing more blood into the muscles fibers.

If, over an extended period of time, an organ needs more oxygen,it stimulates, via growth factors, the blood vessels in the organ to grow[2, 12]. This is another example of how the impulse to change andadapt comes from the periphery. The whole circulatory system, fromcenter to periphery, is involved in getting more blood into the tissuesthat need it.

When the blood moves through the organs, it is continually chang-ing. After we’ve eaten, for instance, the blood passes through theintestines and takes up nutrients. The blood then enters the liver,which draws nutrients out of the blood. The liver also detoxifies theblood, removing, for example, bacteria or alcohol. The blood ascendsto the right side of the heart and then enters the lungs. There the


blood spreads out in fine capillaries where it is enriched with oxygen.This oxygen-rich blood returns to the left side of the heart and then,via the systemic arteries, enters into all the organs of the body. In eachorgan something unique to that organ happens to the blood. In thebrain, large amounts of sugar and oxygen leave the blood. The kid-neys remove metabolic waste products and water from the blood, butalso secrete hormones that regulate the production of red blood cells.The blood is truly a special fluid in its ability to take in and give offsubstances that it moves through the body. It is in unceasing changeand thereby helps the body maintain its physiological balance andcoherence.

The blood spreads out into all recesses of the organs and into theperiphery of the body via arteries and capillaries. Through the capillar-ies, exchange of substances occurs. The blood then recollects in theheart via the veins. We thus need to think of the circulatory system as apolarity of center and periphery connected by movement. The periph-ery is an active and not passive part of the circulatory system. Onerecent discovery shows an unexpected kind of activity. Scientists discov-ered that the peripheral blood vessels, before they are fully functionalin the embryo, induce the development of organs like the pancreasand liver [19]. Evidently, the circulatory system has its mediating rolealready at a very early time.

Changes in the blood’s pressure, viscosity, warmth, and biochemicalcomposition are communicated to the heart. This communication ismediated by the nervous system, hormones, and heart and blood ves-sel sensory receptors. The heart therefore exists as a perceptive centerfor the body via the circulation. Steiner spoke of the heart as a senseorgan for the organism, enabling it to perceive what transpires in theupper and lower poles of the body [21].

The heart does not just perceive what comes to it via the blood. Italso alters its activity. We’ve discussed how it alters its volume and beat-ing rate when more blood is needed in the body. In the 1980sresearchers discovered that the heart secretes a hormone in responseto the changing consistency of blood. If the blood is too viscous, theheart secretes this hormone (natriuretic peptide hormone) into theblood, and the hormone stimulates the kidneys to secrete more waterinto the blood. With time researchers will probably discover ever more


ways in which the heart functions as a perceptive and adaptive centerof our bodies.

One further feature of the interplay of heart and peripheral circu-lation we shouldn’t overlook is the maintenance of body warmth. AsLiesche points out, only the warm-blooded mammals and birds havethe completely four-chambered hearts (see chapter 5 in this book).The internal differentiation of the heart corresponds to the organ-ism’s ability to maintain a high constant body temperature despite rad-ically fluctuating inner and outer conditions. The heart muscle itself isa source of warmth for the blood, while the peripheral circulation canexpand and contract to give off or contain warmth.

Considering these diverse functions lets us recognize qualities ofthe heart’s activity that are overlooked when we focus too exclusivelyon its role in blood movement. This more comprehensive view showsthe heart to be a receptive, perceptive center that continually modu-lates its activity in accordance with the needs of the whole organism.

Into the Soul

It’s illuminating to think of the many words and expressions in theEnglish language that relate to the heart. Here are a few:

Heartfelt

Heartless

Hearty

Heartrending

Heartbreaking

Heartache

Fainthearted

Lighthearted

Heartsore (sore hearted)

Wholehearted

Heart-to-heart

Take heart

Take that to heart

Have a heart

Lose heart

Heavy heart

Warmhearted

Coldhearted

Hardhearted

Heart sick (sick at heart)

Search your heart

Put your heart at rest

Near to my heart

You are all heart


When you go through each expression and feel it, you enter a veryrichly-nuanced world. The feelings that are associated with theseexpressions are often deep (heart sick, heart-to-heart) and span polari-ties (cold and warm hearted; faint and light hearted, and so on). Theyare mostly related to feelings that touch or encompass our inner coreand are central to us. It’s one thing to search your brain for somethingor to put your mind to something and a very different matter to searchyour heart for something or put your heart into it. What comes fromthe heart is authentic and whole. The heart is literally in-dividual; it isunity and when that unity loses its center or begins to dissolve, it’s,well, heartrending.

The quality of warmth is central to the heart. Someone who isheartless is also cold-hearted. When we have a heartfelt concern, thensoul warmth streams out from us, but we remain part of this warmthstream (it doesn’t leave us and dissipate). When we take heart, thenthe warmth enkindles our courage. (The word courage comes fromthe French and is related to the word heart in French (coeur) and inLatin (cor).) And when we’re gesturing to someone to take heart, wemight emphatically raise up our arm and ball up the fist in front of ourchest. Taking heart means gathering at our center and from thereexpanding into the world through our actions.

Not only the heart moves between the polarities of contraction (sys-tole) and expansion (diastole). Rhythmic movement between poles,and mediating and balancing between extremes, characterizes the cir-culatory system as a whole. The blood gathers in the heart and thenflows out into the periphery, changing and exchanging with thisperiphery, and then moving back to the center.

When we’ve grasped the circulatory system qualitatively in this way,it’s not surprising to discover its intimate connection to our inner lifein feelings. Feelings of awe and love allow us to flow out into the world.We connect, give and learn from the world and bring the fruits of thisinteraction back to a center. We experience satisfaction and content-ment. Our joy leads us back into the world. Or our experience of theworld might enkindle fear, anger, or even hate. We draw back into our-selves when such feelings capture us, and then the healthy oscillationof the soul between inside and outside, between self and other, is dis-turbed. Just as we can become completely isolated through hate, so


also we can lose ourselves in unceasing rapture. It’s clear that the maindanger in modern culture is getting caught in feelings of antipathy likehate and anger; we tend much less toward losing ourselves in expan-sive feelings (if we don’t take into account alcohol and drug-inducedexperiences).

The healthy life of the soul depends, as does the circulation, oncontinual movement, on the ability to flow out and gather in. Or wecan also speak in terms of the other middle system in our bodies, therespiratory system: we need the ongoing pendulum swing betweenbreathing out and breathing in.

With progress in developing relatively noninvasive devices torecord physiological processes, it has become easier to demonstrateoutwardly what we all experience from the inside, namely, that ourfeeling life is directly connected to our mental and physical wellbe-ing. People were asked, for example, to self-induce feelings likeanger or compassion by imagining some previous situations in whichthey had the feeling. There were marked changes in heart activity([7, 15]; see Figures 6 and 7). Our soul life and physiology are insep-arable.

It is well known how stress (which means we are inwardly drivenand contracted with little inner breathing room—our soul can’toscillate) has its physiological correlate in hypertension, where theblood, like the soul, is under abnormally high pressure. A Swedishstudy found that women who lived alone, had very few friends, andalso no one to call on if they needed help, tended to have heart ratesthat varied very little over the course of the day [16]. Such low varia-tion in heart rates is correlated with heart disease susceptibility andearly death. Less socially isolated individuals have a more variedheart rate, corresponding to their more varied lives that include moresupport from other people. Here again we see the healthy gesture ofmovement and interaction, while isolation brings not only emotionalmonotony but also has tangible effects on the circulatory system andon health.

Clearly, the path to real understanding and to a comprehensiveapproach to health involves seeing bodily processes as an expressionor outer aspect of what we are inwardly. We need to get beyond consid-ering or treating the body as a thing by itself.


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Conclusion

The kind of picture of the heart and circulation we carry within ushas consequences. First, of course, there is the question of truthfulness.Mechanical models may be helpful to understand partial functions ofan organ or system, but when they become exclusive, the partial truthbecomes falsehood, because we end up making the heart much lessthan it really is. If we are aware of this problem and strive for a many-sided and multi-leveled view of the heart and circulation, then we canbegin to approach its many-sided reality. Of course our picture will notbe adequate, but it will be open-ended so that the depth and breadth offull-blooded reality are fully recognized, if not yet understood.

The pictures we carry within us determine how we view ourselvesand the world. They bear a qualitative stamp. One image is that of acentral power center that forces blood through the body and therebymaintains the body. This is, if you will, an egocentric view of the heart –the forceful doer around which things revolve. The pump just keepson working until it wears out—or, as in the case of the artificial heart,keeps beating even when the person has died.

I couldn’t help having ambivalent feelings reading articles in thesummer and fall of 2001 reporting on the first patients to receive theAbioCor artificial heart, which completely replaces the patient’s heart.On the one hand, I could only marvel at the technology and surgicalability of the doctors. On the other hand, I was disconcerted by the wayin which fascination with the machine and technological progresscame so starkly to foreground.

Mr. Robert Tools was the first patient to receive the AbioCor artifi-cial heart. After the operation in July, Mr. Tools recovered quite welland was able to leave the hospital. He suffered a stroke on November11th. Patients with an artificial heart are always susceptible to strokes,because the blood more easily clots when it comes in contact with theartificial material of the valves. Normally a patient receives blood thin-ners to prevent clot-formation, but this was not possible in Mr. Tools’case, since he had a tendency to bleed internally.

After the stroke, Dr. Laman Gray, who carried out the surgery,reported that Tools’ condition “is probably a little better than a personwith a [real] heart, since we don’t have to worry about the heart itself”


(New York Times, November 15, 2001). Gray went on to comment aboutanother patient who had received the AbioCor artificial heart. Thispatient was making slow progress, due to a high fever that may havedamaged his organs, but, as the reporter paraphrases Gray, “Mr.Christerson’s [artificial] heart has been working well” (ibid.).

On November 30, Mr. Tools died due to internal bleeding. The LosAngeles Times reported (December 1), “‘Tools’ death in no way meansthe experiment failed,’ said Dr. Mehmet Oz …. Indeed, Tools’ doctorsnoted that the heart continued to beat flawlessly even as he died.”Here we see the mechanism enthroned in a sad separation from theperson. The pump still continues to beat as if nothing had changed,while the person dies. And as long as you focus on the mechanism, andthe pump continues to work, the experiment cannot be called a fail-ure, although the patient died.

Very different is the view of the living, dynamic heart and circula-tion. Here we see give and take, and continual change and adaptationthrough interactions. We see a dynamic, perceptive center that main-tains coherence and integrity. This image is not only truer than themechanical one. It also imbues us with a sense of connectedness to ourimage of what it means to be human. From birth till death, the livingheart shares in our life as ensouled beings.

References and Bibliography

1. Benninghof, A. and K. Goerttler. 1980. Lehrbuch der Anatomie des Menschen,Band II. 13th ed. Munich: Urban & Schwarzenberg.

2. Carmeliet, P. 2001. Creating unique blood vessels. Nature 412: 868.

3. Edwards, L. 1982. The Field of Form. Edinburgh: Floris Books.

4. Goethe, J.W. 1988. Scientific Studies. Ed. Douglas Miller. Suhrkamp, NewYork.

5. Gray, H. 1901 (1977). Anatomy, Descriptive, and Surgical (“Gray’s Anatomy”).New York: Bounty Books.

6. Guyton, A. 1971. Textbook of Medical Physiology. Philadelphia: W.B. SaundersCompany.

7. IHM Research Update Vol. 2, No.1. Publication of the Institute of HeartMath,Boulder Creek, CA.

8. Katz, A. 1992. Physiology of the Heart. 2nd Edition. New York: Raven Press.


9. Kilner, P. 2002. Flow through the Heart. The Golden Blade 2002, pp. 39-43.East Sussex, UK: The Golden Blade.

10. Kilner, P. et al. 2000. Asymmetric redirection of flow through the heart.Nature 404: 759-761.

11. Lammert, E. et al. 2001. Induction of pancreatic differentiation by signalsfrom blood vessels. Science 294: 564-567.

12. LeCouter, J. 2001. Identification of an angiogenic mitogen selective forendocrine gland endothelium. Nature 412: 877-884.

13. Marinelli, R. 1989. The spinning heart and vortexing blood. Newsletter of theSociety for the Evolution of Science 5 (1): 20-41.

14. Marinelli, R. et al. 1995. The heart is not a pump: a refutation of the pres-sure propulsion premise of heart function. Frontier Perspectives 5(1): 15-24.

15. Matsumoto, K. et al. 2001. Liver organogenesis promoted by endothelialcells prior to vascular function. Science 294: 559-563.

16. McCraty, R. et al. 1995. The effects of emotions on short-term power spec-trum analysis of heart rate variability. The American Journal of Cardiology 76:1089-1093.

17. Motluk, A. 1999. Lonely hearts. New Scientist 20 February, p. 23.

18. Pettigrew, A. Bell. 1908. Design in Nature. Volume II. London: Longmans,Green and Co.

19. Seydel, C. 2001. Organs await blood vessels’ go signal. Science 293: 2365.

20. Singer, C. 1931. The Story of Living Things. New York: Harper and Brothers.

21. Steiner, R. 1999. Introducing Anthroposophical Medicine. Chapter 2. Hudson,NY: Anthroposophic Press.

2

T h e P o l a r i t y o f C e n t e r a n d P e r i p h e r y

i n t h e C i r c u l a t o r y S y s t e m

H E I N R I C H B R E T T S C H N E I D E R

THE FUNCTIONS OF the human heart, blood, and circulatory system areintimately bound up with the essential nature of the human being.When we ask, for example “What is the significance of blood pressurefor human consciousness?” we look far beyond the mere biology ofblood circulation. Similarly, the question “How do organic metabolicprocesses interact with the movement of blood?” is also broader thana merely mechanistic concept of physiology. Here we are interestedin the quality of living processes and substances as opposed to thosein nonliving nature. We are interested in how these living processesare involved in the transformation of human intentionality intohuman action.

We soon discover that our contemporary language provides no sup-port in dealing directly with such questions. In this essay, therefore, wewill attempt to link certain insights of natural science with psychologicalself-observation so that they mutually illuminate each other. The objectof our search is the deeper language of nature that expresses itself inthe organic world and that ultimately informs human experience.

The Po la r i t y o f C en te r and P e r iphe r y in th e C ir cu la t or y S y s t em 2 3

Blood Pressure and Blood Flow in the Arteries

Figure 1 compares the flow of blood in the arteries, starting nearthe heart and moving toward the periphery, with blood pressure. Sur-prisingly, the curves (waveforms) are not only different, but in manyrespects polar opposite to each other. This indicates that one mustclearly distinguish between the flow of blood and the pressure createdby the arterial walls as between two very different phenomena that areoften viewed as being one and the same thing.

Let’s begin by looking at blood flow (Figure 1, bottom curve). Nearthe heart, in the ascending part of the thoracic aorta (in the graphsimply called Aorta ascendens), the blood does not simply rush in astraight line through the vessel. Rather, it first moves very rapidly and

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then coils backward (indicated by negative numbers in the graph).1

Then the blood moves imperceptibly until the next heart beat when itagain leaves the heart. From this we learn that the movement of bloodin the ascending part of the aorta and to lesser extent in the descend-ing part of the thoracic aorta (in the graph simply called Aorta thoraca-lis) clearly has three phases: forward, backward, and resting. Theresting phase of flow corresponds to the portion of the curve that runsroughly parallel to the zero line, i.e., the blood’s flow velocity isapproximately zero. As the blood moves through the abdominal aortaand into the upper portions of the femoral (upper leg) arteries, thisthree-phase rhythm persists but is gradually transformed. The speed ofblood flow decreases, while the resting phase is progressively replacedby forward flow. Simultaneously, the reverse flow slows (the originallydeep notch in the flow velocity curve flattens out) until finally, in thelower leg, there is no more reverse flow.

Just as we usually (and erroneously) think of blood flow being aconsistent forward flow, we usually imagine the pulse (arterial pres-sure) to be the same throughout the arterial system. But this is not thecase. The flow of blood is very fast near the heart and slows toward theperiphery. In contrast, both peak blood pressure and, to a largerextent, amplitude increase towards the periphery, while the meanpressure decreases very little (see top of Figure 1). Only in the arteri-oles (small terminal arteries with thick muscular walls) is there amarked drop in both peak and mean pressures (dotted lines).

Moreover, as the curve in the peripheral arteries shows, within onepulsation the blood pressure rises strongly and then drops and rises asmall amount again before the next pressure wave. This two-peaked

1. Editor’s note: There are several kinds of flow-recording devices. The most commonlyused today is an ultrasonic or a Doppler probe. Its operation is based on the principle ofemission of low frequency sound, which is “beamed” at a certain angle towards theblood vessel. The sonic signal is reflected from the moving corpuscular elements of theblood and converted into an appropriate waveform. Were the flow steady, that is, non-pulsatile, the recording would be a straight line. The waveform produced by a mechani-cal pump would have the form of a repetitively occurring sinus wave. Since the blood isejected from the heart in vortex-like spiral pattern a more complex waveform results.Whenever the spiraling blood flows towards the probe, a positive or upward recordingresults; when the flow is away from the probe, a negative deflection is recorded.


pressure curve can also be seen in the arteries near the heart. In fact,the two peaks are highly characteristic for human arterial pressurecurves in general, but near the heart the double peak is not verydefined, where it could be viewed as a single peak with a little notch inthe middle. In contrast, the peripheral pressure curve is so deeplydivided into two peaks that its shape resembles strongly the blood flowcurve near the heart that also has two deeply separated peaks. Thechanging shapes of the waveforms in blood flow and blood pressurefrom the center toward the periphery are polar mirror images of eachother. This means that the rapid, three-phase blood flow near theheart occurs in the context of lower blood pressure amplitudes and asmoother pressure curve, while the slower, more constant blood flowin the periphery is bound up with higher pressure amplitudes and atwo-peaked pressure pulse.

There are further contrasts between blood flow and blood pressure.In the case of flow velocity waves, the curve represents the same volumeof blood as it moves from the heart toward the periphery. In contrast,the pressure curve is the result of the movement of a wave of pressure,which is not identical with the movement of a certain volume of blood.An average of 0.2 seconds after the blood flows from the heart into theaorta, the corresponding pressure wave can be felt in the foot. Mean-while, the blood that left the heart at the same time has traveled only asfar as the abdominal aorta. The pressure wave quickly dissociates itselffrom the cardiac cycle, moving toward the periphery with a speed up toten times that of the ejection volume. Meanwhile the flow velocity ofthe blood, which was not high even at the moment of ejection,decreases to a third of its original value. As the body ages, this contrastbecomes even sharper. The speed of the spreading pressure waveincreases steadily, while the flow velocity of arterial blood decreases.

It is a mistake to interpret the typical shapes of arterial flow andpressure curves as coincidences of physics. The graphs in Figure 2compare healthy and pathological blood flow in the femoral artery.Only diseased arteries produce a simple curve with no reverse flowphase—that is, the type of flow considered desirable in mechanical sys-tems. In contrast, healthy arteries produce the typical three-phase flowcurve that first rises up, then dips significantly below zero—indicatinga period of reverse flow -- and finally shows a phase of rest at its end.


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Figure 3 depicts the same phenomenon with regard to blood pres-sure. Only diseased arteries produce a simple pressure curve, while ahealthy arterial pressure curve has two peaks. Just as the soundboard of aviolin amplifies the sound of its strings, the healthy arterial system ampli-fies the pulsating stimuli of the heart. In high-performing athletes, thedouble peak in the arterial pressure curve is even more pronounced than

in average, healthy individuals. Conversely, asshown in Figure 4, a sclerotic arterial system(which most closely resembles a mechanicalmodel) functions by applying strength butlacks the principle of resonance.

Thus if we insist on comparing thehuman physiology to a mechanical device, astring instrument is a far more appropriatechoice than a pump. Applying this meta-phor, the arterial system constitutes the

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resonating body of the violin, and it is not surprising that patients witharteriosclerosis eventually die of cardiac arrest. Imagine a musicianattempting to fill a concert hall with the meager sound of a violin withonly strings but no resonating body! If the heart is a violin string, thearterial system is its body, and both together form the Stradivarius itself(at least in a healthy person), the musical metaphor is surprisingly apt.Figure 4 shows that a healthy double-wave pulse corresponds to a dou-bling of the heartbeat, repeating it, as it were, in a higher octave.

The arteries respond to pressure exerted by the blood by contract-ing, and they relax whenever the pressure drops. This activity is prima-rily autonomous in origin, independent of the central nervous system.Only secondarily does the central nervous system intervene to modu-late arterial resonance. The arterial system, therefore, is a biologicalsystem that slows down blood flow, increases the pressure wave ampli-tude and transposes pressure pulsations into a higher octave by break-ing each pressure curve into two peaks. In other words, it is both abiological flow resistor and a biological pressure amplifier, that is, apressure wave resonator.

The arterial system and the left ventricle of the heart form a physio-logical unity known as the high-pressure system, which is characterizedby the development of blood pressure and by the resonance phenome-non in pressure pulsations. The volume of blood in the high-pressuresystem is remarkably small, amounting to only about 15% of the body’stotal blood.

The Polarity of High and Low Pressure Systems

How does the blood in the rest of the body behave? Approximately85% of the body’s blood encounters almost no resistance to its flow,that is, it flows without being under pressure. The so-called low-pres-sure system includes the capillaries, the venous system, the right sideof the heart, pulmonary circulation, and the left atrium. Under nor-mal, healthy conditions, the low-pressure system immediately absorbs995 ml of a 1000 ml blood transfusion without causing any increase inits blood pressure. The low-pressure system is the polar opposite ofthe high-pressure system in that it relaxes in response to increasedpressure and contracts in response to a drop in pressure. It is also


capable of counteracting pressure (that is, favoring pressureless flow)without recourse to central nerve activity.

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In the veins, pressure pulsations do appear, but they characteristi-cally run counter to the flow of blood, as demonstrated by the exampleof the internal jugular vein in Figure 5. The oscillations are created bypressure waves coming from the heart, against the blood stream. Clearly,therefore, although the fundamental distinction between the phenom-ena of flow and pressure persists in the venous system, they are verydifferent there than in the arterial system. To give another example,the many valves of the venous system in the lower body regions elimi-nate the possibility of the reverse flow phase typical of blood move-ment in the arterial system.

In comparison to veins, arteries are highly consistent in shape. Thealmost circular cross section of their internal space is maintained notonly by high internal blood pressure but also by a force that is uniqueto, and generated by, the arterial system itself, namely, the forceexerted by strong walls of muscles and connective tissue. The tendencyto create a self-contained inner space in the arteries is exceeded onlyin the strongly muscular heart with its unique movement cycle and stillmore restricted (i.e., valve-enclosed) space for blood.

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In contrast, the forces that shape the venous system and its func-tions do not come from the system itself but from its surroundings.In the limbs (the movement pole of the humanbeing), the shape of the veins is determined bylimb movement. The veins are pressed flat atevery contraction of the muscles and expandedby the force of gravity when the limbs are at rest.Figure 6 graphs the blood pressure in a vein inthe lower extremities as a function of limb move-ment. Here too, flow is inversely related to pres-sure. When the flow increases, pressure readingsfall.

Figure 7 illustrates how a vein that serves theskin is incorporated into the fascia surroundingmuscle fibers in the limbs. Clearly, the externalshape of the vein is not specialized for separatinginternal from external processes. On the con-trary, the strands of connective tissue communi-cate movement processes in the limb to theinterior of the vein.

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Figure 8 and 9 illustrate how the shape of the venous system in thehead reflects the circumstances of its environment. The head is theresting pole of the human being and many of its structures are firmand immobile. Taking on this quality, the venous system in the head(the sinus of the dura mater) is embedded in the inflexible tissue

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between the dura mater and the skull. It is polygonal in cross sectionand immobile. Note how differently the shapes of the arterial systemdevelop in the same location. The arteries have muscular walls and thespace surrounding them—the so-called subarachnoid space throughwhich cerebrospinal fluid circulates—functions like a hydraulicdamper and permits the arteries, even those on the underside of thebrain, to maintain a circular cross section with the help of their ownmuscles and internal pressure (see Figure 9). From a morphologicalperspective, we can say that the high-pressure system in human circula-tion has more self-contained forms and spaces, while the low-pressuresystem is more open and receptive to its environment.

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As Figure 10 illustrates, the volume of blood is inversely related tothe tendency to create self-contained spaces and forms in the circula-tory system. Consequently, the relative blood volume of the entireheart (7%) is smaller than that of the arteries (12%). The greaterenvironmental sensitivity of the low-pressure system as compared tothe high-pressure system is also evident in the morphology of theheart. The right ventricle, which in contrast to the left ventricle mustbe considered part of the venous circulatory system, has not only thelarger volume but also the thinner walls typical of veins as opposed toarteries. The left ventricle is significantly smaller, containing approxi-mately 3% of the body’s total volume of blood in comparison to theright ventricle’s 4% (see Figure 11). The thinner-walled right ventriclecan adapt to the shape of the left, which is round and thick-walled incross section.

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Capillary CirculationThe circulatory system’s greatest degree of openness to the environ-

ment, however, is found not in the venous system but in the capillarybed. The walls of the capillary bed are impermeable only to erythro-cytes (red blood cells) and blood platelets, with two notable exceptions.In the capillary sinuses of the bone marrow (sinus means a blood chan-nel whose boundaries are determined by surrounding tissue ratherthan by the blood system itself), red blood cells enter circulation bypassing through capillary walls. Once the fate of these cells is sealed andthey are destined for breakdown, they leave the blood stream and enterthe spleen and liver, again by passing through capillary walls. Besidesthe two regional specializations just mentioned, the relative isolation ofred blood cells in the capillaries is generally maintained not by the cap-illary walls themselves, but rather by a finely tuned biochemical balancebetween blood clotting and clot dissolving (fibrinolytic) factors. If theblood clotting system fails, red blood cells seep out of the capillary bed,causing uncontrollable internal bleeding even when no injury hasoccurred. In contrast, if fibrinolysis fails, generalized clotting of theblood occurs, bringing circulation to a standstill. Thus one of the chem-ical activities of blood is a balancing act between the two extremes ofuncontrolled bleeding and coagulation.

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Figure 12 shows that in the capillaries, the prevailing frequencies ofpressure waves correspond in order of magnitude to the cardiac cycle,although the amplitudes are small and they are out of phase with theheart. The amplitude of pressure pulsations decreases steadily fromthe arterioles (A), where the pressure is approximately 20% of meanarterial pressure, to barely 5% in the capillaries (D). The regular oscil-lation seen in the arterioles becomes increasingly amorphous andalmost flat. The effects of the high-pressure system’s pressure pulsa-tions are still evident, although clearly weakened, in the capillaries. Incontrast, as Figure 13 illustrates, physiological blood flow in the capil-laries is highly independent of anything correlated with the move-ments of the heart, since there is absolutely no relationship betweenthe cardiac cycle and the flow velocity of the blood in the capillariesthemselves. Here we find flow pulsations that are due to spontaneouscontractions of the arterioles (vasomotion) and occur at rates of 0.5 to

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20 per minute. In the actual capillaries themselves, which are not con-tractile, these pulsations decrease dramatically, to less than 5% of theaverage rate of blood flow.

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At a tenfold increase in scale (Figure 14), it becomes apparent thatthe continuous flow of blood in the capillaries (suggested by Figure12) is an illusion. The two upper graphs show nothing new but simplyillustrate that the effects of arteriole vasomotion are measurable evenin the capillaries if the recording device is sensitive enough. The low-est chart shows that the forward flow of blood can also cease. Thus wecan state conclusively that blood flow in the capillaries is largely inde-pendent of the heart. In the heart, momentarily, forward blood flow isinterrupted (in the isovolumetric contraction phase). This is accom-panied by a very significant increase in blood pressure. In the heart,therefore, cessation of flow and high blood pressure are mutuallydependent. In contrast, in the capillary bed cessation of flow occursperiodically without producing pressure. Our further studies will eluci-date the meaning of this “obstinacy” on the part of peripheral circula-tion and explore the domain of the forces that the capillaries mustuse in order to generate flow that is independent of both the heartand blood pressure.

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The spatial configurations of capillary walls vary greatly, dependingon the species, the organ, location within an organ (i.e., proximity toneighboring organs), and especially on functional status—that is, on the

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specific metabolic processes of the surrounding tissues. Within this rangeof variation, the following types of capillary walls have been recognized:

1. The “continuous” type. There are no gaps in the walls (endotheliallayer), but they are frequently punctuated both by villi that emergeand disappear rapidly and by small bubbles flowing through the tis-sue. The first section on the left in Figure 15 illustrates this type,while the second shows a variation characterized by “basal feet” orprotrusions that grow into the surrounding tissue, penetrating thebasal membrane, and may then disappear equally quickly.

2. The “porous” or “fenestrated” type. Here, too, flowing bubbles arefound in the plasma between the fenestrations, which measure0.03-0.1 mm, depending on the organ, and appear and disappear(Figure 15, center) depending on the metabolic activity of the sur-rounding tissue. The basal membrane is still present.

3. The “fragmented” type. There is no basal membrane (Figure 15,right), and the endothelial cells are generally not connected. Intercel-lular and intracellular holes (practically indistinguishable from eachother) often exceed 1 mm in diameter and are extremely frequent.

According to some anatomists, the value of dividing capillaries intothese three types is purely academic because all possible transitionalforms can be observed. We will not immediately subscribe to this opin-ion, however, because there is some functional basis for this classifica-tion. For example, the protein content of lymph (the fluid that fills thespace outside the capillary walls and exchanges substances with thecontent of the capillaries) varies considerably from organ to organ:

Brain: no lymph (cerebrospinal fluid: 0.15-0.45 g protein/liter)Skin: 1 g protein/lSkeletal muscles: 2 g protein/lHeart muscle: 3 g protein/lIntestines: 4 g protein/lLiver: 6 g protein/l

As we see from this series, the brain has no lymphatic spaces sur-rounding its capillaries, while liver lymph contains nearly as much pro-tein as blood plasma.


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A magnification of a liver capillary (Figure 16) shows why theexchange of substances between capillaries and lymph is possible inthe liver. As we mentioned earlier, old red blood cells pass throughcapillary walls into both the liver and the spleen, where they are bro-ken down. During anticoagulant therapy to dissolve blood clots, theliver is the first place where fibrinolysis may get out of hand and allowblood to enter the tissue. Fibrinolysis experts consider this phenome-non on a small scale harmless, and some even see it as nothing morethan a variation on normal liver status.

In contrast, fibrinolysis-induced bleeding inthe brain is much feared and catastrophic. In themicroscopic image of a brain capillary in Figure17, the terminal fibrillar processes of the so-calledastrocytes closely surround the capillary wall,forming a membrane-like net that leaves no spacefor lymph. (Astrocytes are neuroglial cells thatsupply the rapidly depleted nerve cells with nour-ishment.) In functional terms, this membraneconstitutes the blood-brain barrier, which prevents

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ions (electrically charged particles) and highly hydrated compounds(such as carbohydrates) from passing into the brain. Sugar, the onlynutrient that enters the brain, must be actively transported across thebarrier. Mainly water, gases, and narcotics (which are fat-soluble) passthrough it freely.

Microcirculatory and Lymph System

As we look at Figure 18, let’s recollect that as a rule, circulatorystructures that create self-contained spaces have small volumes andhigh blood pressures, while the reverse is true of structures that areopen to their surroundings. This view is supported by the fact that thevolume of the left side of the heart is less than that of the right, andthe total volume of the heart is less than that of the arterial system,which in turn is less than that of the venous system. The volume of thecapillary system, however, with only 16% of the body’s total volume ofblood, is significantly less than that of the venous system (65%) andnot much more than the combined volume of all the arteries (12%).In terms of the law of spatial relations we believe to have discovered, isthere a contradiction here between the apparent environmental open-ness of the capillary system and its relatively low volume?

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As a consequence of recent insights into the capillary system’s highdegree of environmental responsiveness, the classical concept of the“capillary bed” or “terminal circulation,” which included only the cap-illaries, has been expanded and replaced by the term “microcircula-tory system.” The microcirculatory system encompasses not only allblood vessels with diameters of 0.3 mm or less and their contents butalso the entire extracellular matrix—that is, the spaces between thecells of tissues or (to put it in lay terms) the lymph and the peripheralportions of the lymph drainage system (i.e., the lymphatic capillaries).The extracellular matrix, however, contains approximately ten liters ofwater, more than twice the fluid volume of blood plasma (approxi-mately 3.5 liters). This fluid volume is surpassed only by the volume offluid contained within all the cells of the human body (a total ofapproximately 30 liters).

Thus the blood in the capillaries, at 16% of the body’s total bloodvolume (approximately 1.12 liters), constitutes only a relatively smallpart of the fluid volume of the entire microcirculatory system. Withinthis system, which otherwise transports only colorless lymph, red-col-ored blood represents the pole of a self - contained fluid.

Even the extracellular matrix, the lymph-filled space between theconnective tissue cells is subdivided within itself. 20% of the water inthe extracellular matrix is bound to connective tissue fibers (col-lagen), while 80% consists of films of fluid moving over the cell sur-faces.

Figure 19 summarizes some of our present-day knowledge aboutthese special fluid movements outside the capillaries. Most recentinsights into the fine structure of the matrix of the extracapillary fluidcompartment suggest a three dimensional network of collagen andelastic protein fibers filled out by colloidal organic substances.2 Thecolloidal state of organic substances filling out the extracapillary

2. According to Hauck [10], especially elastic connective tissue fibers function as con-ductors for film-like fluid movements in the intercellular matrix. The transportation ofsubstances via this pathway is much faster than diffusion. Collagens do not show thisconductive property. When, in the course of aging, elastic fibers are consecutivelyreplaced by collagen fibers the transport of substances is markedly slowed down in theextracapillary matrix [14].


fibrillar matrix network is presently understood as an equilibrium ofprocesses simultaneously working in opposite directions, that is,towards coagulation and liquefaction (colliquation) of large solublemolecular proteins. Both of the polar processes, working at the sametime, neutralize each other, creating a very high level of responsive-ness. Within this sensitive equilibrium there are states of a relativelyhigher viscosity that can actually form little “gel-islands” (stippled areasin Figure 19). Between these islands, channels of relatively less viscoussubstance form (see the channels of broken lines in Figure 19).

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These conditions make the shape of the extracapillary fluid com-partment extremely inconstant and highly susceptible to many differ-ent kinds of external influences. Even emotional and meteorological

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factors (major changes of the weather) can influence the microcircu-lation of the extracellular matrix temporarily [13]. We then experi-ence the ups and downs in our sense of well being in everyday life.But these factors can also play a role in chronic conditions such asrheumatic disorders.

Although the shape of the extracapillary fluid compartment isextremely inconstant, eventually its channels lead into tiny, but never-theless persistent lymphatic capillaries.3 This is why the former chan-nels are also called prelymphatic structures. These inconstantprelymphatic channels also interact with a special kind of slowly fluctu-ating fluid around the blood capillaries called the paravasal plasmamantle (see the hatched sheaths around the capillaries in Figure 19).In this way the prelymphatic capillaries are intimately interconnectedwith the red blood system.

With regard to fluid movement, there is a noteworthy differencebetween the prelymphatic structures and the paravasal plasma mantle:Whereas the fluids in the paravasal plasma mantle move parallel to theblood capillaries, the direction of movement in the prelymphatic struc-tures is approximately at right angles to the capillaries. And as the fluidsof the paravasal plasma mantle move very slowly alongside the bloodcapillaries, they communicate intimately not only with the prelymphaticstructures, but also with the flow of plasma inside the blood capillaries.

This interplay is accomplished by a special phenomenon calledlaminar flow. The fluids in laminar flow do not move homogenously,but rather, as the word itself expresses, in sheaths of differing velocity:the relatively highest velocity of streaming occurs at the center of thecapillary, whereas movement gradually becomes slower towards thecapillary boundary until it is extremely slow, if not stationary, on thesurface of the capillary wall. We must therefore imagine two very slow,but nevertheless quite voluminous streams running parallel to eachother, one inside, the other outside the capillary wall. The one outsideis connected to the prelymphatic structures running away from the

3. Presently the system of lymphatic capillaries is considered to be completely opentowards the prelymphatic structures. Older concepts of a blind ending (or beginning)of the lymphatic capillary system were due to anatomists’ limitations of retrograde fillingtechniques [6].


blood capillaries at approximately right angles. The other, runninginside the blood capillaries, takes part in the system of laminar flow.With its laminar flow the circulation system has a system of living regu-lation that, as we pointed out before, is by no means confined to a lim-ited anatomical space inside the capillary wall, but opens up to a richworld of fluid movements.

Thus the polar opposite of the heart’s activity is not the capillarybed but intercellular microcirculation interacting with laminarstreams. One pole of the circulatory system is the lumen of the heart asa circumscribed organ of flow resistance [Stauorgan], where pressureis created in a muscular internal space enclosed by valves. The otherpole consists of the wealth of different kinds of fluid processes in theperipheral circulation, where films of colorless fluid, balancedbetween the liquid and gel-like states, move around and between cells.These fluids connect all the different organs of the human body,including the tissues of the heart itself.

Gaspare Aselli, professor of anatomy and surgery in Pavia in the sev-enteenth Century, discovered the lymphatic vascular system. His dis-covery came at a time when science was taking its first steps towardunderstanding the minute details of the human body. It sheds light onthe ideas discussed above, showing the periodic cessation of circula-tion accompanied by loss of pressure. There can be no doubt, in thiscase, that the cause of the cessation lay in the peripheral circulation.Aselli writes:

On July 23, 1622, at the request of several friends, I opened the body of a healthy and well-nourished dog in order to trace the pathways of the recurrent nerves. Having done so, I prepared to observe the movements of the diaphragm. With this in mind, I opened the abdominal cavity and moved the stomach and intes-tines aside. At that moment I saw a quantity of thin, gleaming white strands whose many branches extended over the entire mesentery and intestines. At first glance I thought these strands to be nerves and paid no particular attention to them, but I soon discovered my error, for the nerves leading to the intestines were differently structured and followed different routes. Deeply moved by this discovery, I stood there in silence for a


while. A few days previously, by some coincidence, I had read a paper by Johannes Costacus on these same issues, and now I mentally reviewed the disputes of anatomists about the function of mesentery veins. I roused myself and punctured one of the thickest strands with the point of a scalpel. No sooner had I done so than I saw a milky or creamy fluid emerging from the incision. At this observation I could no longer restrain my plea-sure and cried out ‘Eureka,” urging my friends to fully appreci-ate the unaccustomed show. They were visibly impressed with this new discovery. Our pleasure was short-lived, however. The dog expired and suddenly, under our hands and before our eyes, the gleaming, fluid-filled vessels disappeared almost with-out a trace.

Deeply disappointed, I resolved to attempt a second experi-ment. The next day I procured another dog and promptly pro-ceeded to cut it open, but the most careful investigation revealed not a single white vessel. Disheartened, I was ready to believe that my discovery of the previous day had been, as Galen says, an infrequent anatomical occurrence. But then I remembered that the second dog, unlike the first, had had nothing to eat or drink for a long time before the experiment, and I rightly assumed that fasting had caused the disappear-ance of the vessels in question. I therefore undertook a third experiment with still another dog, which I cut open on July 26, six hours after it had eaten its fill. All of the phenomena I had observed in the first experiment repeated themselves with this third animal, the only difference being that the vessels disap-peared even more quickly. This repeated success confirmed my assumption [2].

Aselli was later able to confirm the presence of chyle-filled abdomi-nal lymphatic vessels in a number of different mammals whenever theanimals had eaten recently. In 1627, Nicholas Peiresc reported thesame phenomenon in a condemned criminal who had eaten shortlybefore his execution.

Aselli’s account is reproduced here in such detail because of its veryrelevant treatment of a theme that we first encountered in the example


of blood flow in the capillaries. Lymph demonstrates much more drasti-cally than blood that in certain parts of the circulatory system, flowdepends on the organism’s metabolic functions. When his experimentalanimals had not eaten, there simply was no lymph for Aselli to discover.

In terms of our view of the dynamic morphology of the circulatorysystem, it is obvious that in general the vessels of lymph must be moreopen to their surroundings than those of blood. It is fitting that lym-phatic capillaries—that is, the very finest beginnings of the lymphdrainage system in the “open” lymphatic space between tissues—haveneither basal membranes nor pericytes and are therefore in generalmore permeable than most blood capillaries. It is true, however, thatthe lymphatic capillaries empty into lymphatic drainage vessels whosewalls become thicker as their size increases. Ultimately, the largest ofthese vessels have valves like the venous system and also contract spon-taneously, with the frequency of the contractions approximating thatin the arterioles. With regard to flowing blood, or lymph, the zenithof openness to the environment therefore lies in the extracellularlymphatic spaces surrounding organ tissues. Thus it is not surprisingthat once this point of greatest environmental susceptibility ispassed—that is, in the lymph that flows in closed vessels—the volumeof lymph is less. It is estimated that the flow through the main lym-phatic duct that empties into the great veins near the heart amountsto only about two liters of lymph in 24 hours, a quantity comparableto a day’s production of secondary urine, the urine that actually leavesthe body. Secondary urine represents a concentration of a daily pro-duction of approximately 170 liters of primary urine. Analogously, thelymph that is channeled back into the venous system can be seen as asecondary fraction of the much greater volume of “primary” or inter-cellular lymph.

The Circulatory System as a Whole

Figure 20 summarizes the current status of our assessment of theissue of circulation. The circulatory system encompasses all the stagesin a metamorphosis between two polar opposite tendencies. The devel-opment of self-contained spaces is associated with blood; thick-walled,contractile vessels that are round in cross-section; a limited number of


physiological processes; and a small and limited volume. Openness tothe surrounding milieu is associated with lymph; flexible, thin-walledvessels; an almost unlimited scope of physiological processes; and alarge, variable volume. Blood capillaries lie between the extremes ofthis classification system and are “citizens of two worlds.” In the capil-laries, qualities of containment and openness meet and interpene-trate. The left side of the heart is the center of the tendency towardself-containment. The lymph, in contrast, has no center but workstotally from the periphery, from the domain of the extracellularmatrix, forming a bridge between the metabolic processes streaminginto the circulatory system and the centrifugal circulatory activity ofthe heart and arteries.

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As we saw earlier, the circulatory organs most effective in develop-ing pressure are those with thick, dense, muscular walls. These organsare capable of impeding the flow of blood, that is, they function likeflow resistors. Chief among them are the left side of the heart, whosevalves interrupt the forward flow of blood and whose muscular con-tractions create pressure in the bloodstream, and the arteries, which

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amplify the impulses from the heart like a sounding board and repeatthem one octave higher, so to speak. These organs constitute the formor morphological pole of the circulatory system. The capillary system isstill just barely responsive to the effects of cardiac and arterial activity.In the capillaries, the frequency of pressure pulsations is the same asthe heart rate but out of phase and their pressure is reduced to about5% of average pressure. Furthermore, the pattern of pulsations in thecapillaries is chaotic in nature in comparison to their sawtooth-likeregularity in the arterioles (see Figure 12).

In contrast, the part of the circulatory system—namely, the extra-cellular matrix, which moves the greatest volume of fluid—that ismost effective in developing flow is also its most peripheral and openaspect. This competence with regard to flow is already evident in thecapillaries: at 5-20 oscillations per minute, the frequencies of the flowpulsations set in motion by the spontaneous activity of the pre-capil-lary arterioles are clearly different from the heart rate. Capillary flowis so heavily influenced by the extracellular matrix—ultimately, thatis, by metabolic processes in their surroundings—that there are peri-ods of time when all flow ceases (see Figure 13, lower graph), namely,when local metabolism provides no grounds for flow. Local metabolicactivity (the process or physiological pole of the circulatory system),therefore, is the reason for the capillaries’ relative independencefrom the flow pulsations coming from the heart. For example, bothexperimental injection of acid into the duodenum and the naturalentry of acidic chyme increase blood flow by 25% in the liver arteryand by as much as 35% in the capillaries that feed into the hepaticportal vein. When abdominal perfusion is simultaneously restricted,increases in capillary perfusion of working muscles are quantitativelyeven more significant.

Furthermore, as we now know, the blood that flows in the capillarieshas a higher plasma content than the blood in larger blood vessels. Inthe blood in larger vessels, the volume ratio of cells to plasma is approx-imately 40:60. In each separate branch of the capillary system, however,the relative proportions of the red blood cells and blood plasma are dif-ferent. These components often go nearly completely separate waysbecause of phase separation where branching occurs. Thus the “red-ness” of capillary blood is rhythmical rather than constant. Depending


on processes in the immediate surroundings, capillary blood may flowor cease to flow, and when it flows, it may have more corpuscles at onetime and more plasma at another.

In the domain of the capillaries, therefore, mediation between twoworlds (one centrally and one peripherally oriented) creates receptiv-ity to both the process of impeding [Stau] that proceeds centrifugallyfrom the center and the flow that works from the periphery.

The classical conception of red blood circulation as a rhythmicallypulsating cycle linking the heart and the capillaries becomes valid onlywhen it is supplemented by the environmental responsiveness that ischaracteristic of the low-pressure system in general and the capillariesin particular. And yet the image that results is still only half true—i.e.,false—because we need to take into account the large volume oflymph. The flow of lymph is evidently being impelled by metabolicprocesses in the surrounding tissues and not by the heart.

How can we imagine the lymph in relation to the rest of the circu-latory system? Figure 21 attempts a schematic answer to this question.Blood circulation is represented as moving in a circle from the leftventricle through the arteries, capillaries, and veins back to the rightventricle of the heart. In the capillaries, the arc becomes “porous,” as

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represented by the regular gaps, while the thickness of the linesnearer the heart represents the increasingly massive walls of the arter-ies. This blood-carrying half of the cycle is already polar in itselfthrough the high- and low-pressure systems. It is then joined by theperipheral microcirculation (illustrated in the diagram with brokenlines as a flow occurring at right angles to the direction of flow of theblood system). Only the addition of this peripheral flow makes awhole truth out of the half-truth of our classical conceptions of bloodcirculation. The lymph drainage system projects into the extracellularmatrix (where lymph circulates freely), where it is initially extremelypermeable, but ultimately becomes as closed as the venous systeminto which it empties.

The Circulatory System in Relation to the Human I

Arteriovenous anastomoses are shortcut connections betweenarteries and veins that allow large portions of the capillary system tobe shut off from circulation. In lower vertebrates, arteriovenous anas-tomoses are found in internal organs, where their purpose is torespond to metabolic needs (such as the intermittent perfusion ofmuscles) by shifting around relatively large amounts of blood inde-pendent of cardiac activity. But only in warm-blooded animals and inthe human being are anastomoses found on the surface of the body.This clearly correlates with the emancipation of thermoregulationfrom the environment. In birds, these shortcuts are found only in thefeet—in the webbing between the toes of ducks, for example.Another oft-cited example is the anastomoses in the wing membranesof bats. Anastomoses make it possible to concentrate body heat in thecentral part of the body by withdrawing blood from the periphery.Some mammals have anastomoses not only in their digits and earsbut also in parts of the face. This is especially the case in monkeys,that is, in the closest relatives to the human being. Only humans,however, have anastamoses over the entire surface of the body, whichmeans that blood can retreat from the environment to a muchgreater extent in humans than in other warm-blooded species. As aresult, humans have the greatest possible degree of autonomy withregard to warmth.


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Figure 22 shows the distribution of warmth on the surface of thehuman skin during two typical, polar phases in the activity of the ther-moregulatory system. By day, when we are awake, the anastomoses inthe skin are opened, shutting off capillaries on the body’s surface, andthe central area of warmth is restricted to the head and torso. Thisstate of greatest centralization of circulation and body heat is also ourmost alert and self-controlled state with regard to psychological inten-tionality, as is especially evident during mental concentration when thebody is at rest.

Whenever we move our limbs (and to an even greater extent whenwe perform heavy physical labor), peripheral anastomoses are closedand the body’s inner core of warmth expands. This process peaks atnight when we are asleep (Figure 22, right). The anastomoses are closedand the inner core of warmth, along with red capillary blood, soon

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extends all the way to the body’s surface. In sleep, we are most open toour environment with regard to circulation, but our psychologicalintentionality is at its dullest. This state is closer to physical labor than towakeful concentration when the body is at rest, because during workour intentionality is fully directed first to our limbs and then to theobjects in our field of activity, as is especially evident during heavy laboror athletic endurance training. What many endurance athletes enjoyabout their training is the sensation of “intentionality” in their limbs.

The day and night alternations in the human thermoregulatory sys-tem, as well as those between wakeful rest and physical activity, providean image of the activity of the human I itself. By day, when we areawake, we have I-consciousness as beings dwelling within our bodies.The anastomoses are opened, the peripheral capillaries are shut downfrom circulation and the core of internal warmth retreats to the headand torso. Thus anastomoses serve the creation of a self -containedspace in the circulatory system by withdrawing blood from the periph-ery and “centralizing” circulation. This condition promotes and is alsoan expression of concentration.

In contrast, when we fall asleep and lose our I-consciousness,warmth expands to the body’s periphery; warmth promotes dulledintentionality of the expansive “night state.” In this state of conscious-ness, we can experience our I as if it were outside of the body. Wedream, for example, of being able to fly (a picture of a spirit freedfrom bodily gravity) or, quite to the contrary, of not being able to moveour legs (a picture that is the physical consequence of the I not being“in” the body).

Human thinking is characterized less by its rich combining abilityalone than by its high degree of emancipation from the perceptualprocess. For example, chimpanzees in experimental situations havebeen able to assemble several sections of a rod to make it long enoughto reach a banana. They are able to do so, however, only when thebanana and the rod are simultaneously present in their field of vision.They must be able to see the solution to the problem. Human thinkingand memory are, in contrast, often situation-free. We can imagine,remember, and combine images of things that are not in our immedi-ate field of perception. This kind of situation-free memory is a centralfeature of the human I.


The human head, especially the face, remains conspicuously unaf-fected by the diurnal contraction and nocturnal expansion in humanthermoregulation. The rhythmic alternation of the I between day andnight is totally different from the rhythm of the perfusion of facial skin(that is, the alternation between blushing and turning pale), whichreflects how our affective life oscillates between sympathy and antipa-thy or fear and shame. This alternation between blushing and pallor,which is much more rapid than the daily rhythm, reveals the relation-ship between our sentient organization and the circulatory system.When we are unwell, however, facial pallor obeys a different rhythm(significantly longer than day and night) and reveals the relativestrength of our vitality and the blood. The quicker rhythm of blushingand turning pale constitutes a wordless language that speaks to otherhuman beings in social intercourse. The slower rhythm, however,speaks to physicians, who will be able to serve the balance needed byeach individual patient if they learn to artistically “recreate” the polarforces that imbue human beings and apply them methodically in theuse of medications.

The interplay of warmth, blood, feelings and intentionality are allexpressions of the human I. They are tools for human activity, whichencompasses both our conscious thinking and our unconscious will-ing. Human circulation is bound up with the whole human being.

References and Bibliography:

1. Aschoff, A J. 1971. In Gauer, Kramer, Jung, eds. Physiologie des Menschen,Vol. 2. Munich: Urban & Schwarzenberg.

2. Aselli, G. 1627. As quoted in J. Meyer-Burg (1977), Der abdominelle Lymph-kreislauf. Baden-Baden: Witzstrock-Verlag.

3. Barnes, R. W. 1983. Nichtinvasive Untersuchungen von Gefäßerkrankungen. San-doz-Schriftenreihe 1.

4. Benninghoff, A. and Goerttler, K. 1979. Lehrbuch der Anatomie des Menschen,Vol. 2, 12th ed. Munich: Urban & Schwarzenberg.

5. Bockemühl, J. 1982. Bildebewegungem im Laubblattbereich höherer Pflan-zen. In W. Schad, ed. Goetheanistische Naturwissenschaft Band 1: AllgemeineBiologie, pp. 17-35. Stuttgart: Verlag Freies Geistesleben.

6. Casley-Smith, J. R. 1976. The fine structure and function of blood capillar-ies, the interstitial tissue and the lymphatics. In: Ergebn. Angiologie 12.


7. Gaethgens, P. 1982. Mikrozirkulation. In R. Busse, ed. Kreislaufphysiologie,pp. 70-103. Stuttgart: Thieme-Verlag.

8. Ganong, W. F. 1979. Lehrbuch der medizinischen Physiologie. Stuttgart:Springer Verlag.

9. Goebel, T. 1983. Das Herz als Stauorgan. In Ideen zum Herz-Kreislauf-System,pp. 85-109. Stuttgart: Verlag Freies Geistesleben.

10. Hauck, G., et al. 1978. The prelymphatic transinterstitial pathway. J. Lymphol.2: 70.

11. Hauk, G. 1982. The connective tissue space in view of the lymphology.Experientia 38: 1121-1122.

12. Hauk, G.1984. Physiologische Aspekte der Hämorheologie. In Hämostaseo-logie I. Stuttgart: Schattauer Verlag.

13. Heine, H. 1984. Oral communication.

14. Jäger, K. et al. 1979. Videomikroskopische Untersuchungen der Diffusionvon Na-Fluorescein bei der chronisch-venösen Insuffienz. In 2. GemeinsameJahrestagung der Angiologischen Gesellschaften Deutschlands, Österreichs und derSchweiz, Abstract 91.

15. Jungmann, H. 1970. Normale und pathologische Pulsformen. In G. Liebauand E. Pestel, eds. Phänomen der pulsierenden Strömung im Blutkreislauf. Han-nover: Bibliogr. Inst.

16. Schmidt, R. F. and G. Thews. 1980. Lehrbuch der Physiologie des Menschen,20th ed. Berlin: Springer.

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18. Tischendorf, F. 1981. Die funktionelle Struktur der Leber. In L. Wannagat, ed.Leber. Stuttgart: Thieme.

19. Waldeyer, A. 1970. Anatomie des Menschen, Vol. 2, 6th ed. Berlin: De Gruiter.

20. Woernle, M. 2002. Embryology of the Circulatory System. In this volume.

21. Wolff, J. 1971. Ultrastruktur der Kapillaren. In E. Bauereisen, ed. Physiolo-gie des Kreislaufes, Band 1. Pp. 67-98. Berlin: Springer Verlag.

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Fig. 4: During exertion, cardiac output increases as the heart rate increases.

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4

A D y n a m i c M o r p h o l o g y o f t h e C a r d i o v a s c u l a r S y s t e m

W O L F G A N G S C H A D

Introduction

A DYNAMIC MORPHOLOGY of the cardiovascular system must consider notonly the spatial forms of the heart and blood vessels but also the vitalfunctions and, ultimately, the development and evolution of theseorgans. The word “circulation” itself denotes a process rather than sim-ply finished organs.

Different times and cultures have held very different views of thehuman circulatory system. In Greco-Roman times, this system wasunknown, and no one spoke of it. The Greeks and Romans knew thatveins and arteries were morphologically different but did not knowhow they were connected via the capillaries. It was generally assumedthat arterial blood disappeared into the organs, where it was destroyedand ceased to exist. What then emerged in the veins was thought to bea completely new and different substance called “pneuma.” Thisancient Greek word has no real modern equivalent. Although it doesmean “air,” among other things, it is a word so rich in meaning that


today it would also have to be translated as “soul” and “spirit.” Simi-larly, the Latin word spiritus means both “breath” and “spirit,” and theGreek anemos means “wind” (as in “anemone” = windflower), while itsLatin cognate animus means “soul.” In German, Geist (“spirit”) isrelated to Gischt (“spray”). In a way that we no longer experience, earlypeoples heard the voices of the gods in the rustling of the trees andsensed that the most delicate physical substances were very close tosoul and spirit. Thus the word pneuma is impossible to translate when itis used in reference to the venous system. Did the ancient Greeksmean that the veins were filled with air, or were they thinking of theorganism’s soul and spirit components, which to them were just as realas the physical body? In any case, modern science has interpreted thisword to mean that the veins were full of air, and to this day the anatom-ical name of the large veins that return the blood to the right cardiacatrium is venae cavae, “hollow veins.”

Andreas Vesalius (1514–1564), the personal doctor of emperorCharles V, was the first person to systematically investigate human anat-omy via dissections. His book on human anatomy, published in 1543,was the first of its kind and also a graphic masterpiece. Vesalius’ stu-dent, the Italian Realdo Colombo (1510–1559) described the pulmo-nary circulation in 1545. Andrea Cesalpino (1519–1603) wasColombo’s student and coined the term “circulatio” in 1571, applyingit to the pulmonary circulation [4, p. 198].

Many textbooks credit William Harvey with discovering the physicalcirculation of the blood in 1616, during his experiments with partiallyincubated chick embryos [2]. While it is perfectly true that theseexperiments did lead Harvey to formulate his ideas about the circula-tory system, he had no microscope and therefore did not actually seethe capillaries that complete the vascular system [5]. Because bloodvessels on the body’s periphery become too small to see unaided, Har-vey deduced that vessels invisible to the naked eye must lie betweenthe arterial and venous branches of the circulatory system. This deduc-tion, however, was purely theoretical. Consequently, statements credit-ing Harvey with the discovery of blood circulation must be revised. In1661, four years after Harvey’s death, Marcello Malpighi was the first toactually prove the existence of capillaries and hence the continuity ofthe vascular system. Ever since then, the circulatory system has been

Th e Dyna mi c M or pho l o g y o f t h e Car d i ovas c u la r S y s t e m 7 9

viewed as a closed system for transporting fluid, and blood pressurehas been assumed to be due exclusively to the activity of the heart mus-cles within this closed system. According to the prevailing view, themuscular heart functions as a pump that maintains circulation.

But is this theory scientifically tenable? Clinical observation revealsthat patients with intact hearts may nonetheless have circulatory prob-lems and tire very easily [14,3]. Conversely, circulation may be strong inpatients whose hearts do not function normally. Such people, althoughthey may not be able to carry a normal workload, may lead relatively nor-mal lives and can accomplish a great deal if they pace themselves. Thusthe circulatory system is not a passive system of tubes in which the heartprovides the energy. The circulatory system as a whole functions as a sec-ond heart, so to speak, compensating for weakness in that organ.

The clinical details confirm the inaccuracy of the concept of theclosed circulatory system [14]. This is exactly what Harvey suspectedwhen he spoke of tissue gaps (carnis porositates) on the periphery of thecirculatory system. Blood circulation is a closed system only with regardto red blood corpuscles (except in the spleen and in the bone marrow).Unless an injury occurs, these cells spend their entire life span withinthe circulatory system. Once they move out of the bone marrow intothe bloodstream, they remain there for 120 days until they are removedand broken down by the spleen. With regard to blood plasma, however,the circulatory system is not closed. Plasma moves through vascularwalls in capillary networks all over the body. This phenomenon is mostclearly apparent in the kidneys, which would not be able to extractwater and metabolic waste products from the blood if there were not anetwork of half-open capillaries in every glomerulus. All capillaries, notjust kidney capillaries, are permeable to plasma. Where the capillariesbegin, after the arterioles (the smallest arteries), blood fluid soaks intothe surrounding tissue. Where the capillaries approach the venules(the smallest veins), the opposite occurs—fluid from the surroundingtissue is reabsorbed into the blood. This openness means that externalstimulation of peripheral circulation can decisively influence not onlycapillary activity but also circulation as a whole. This fact plays animportant role in therapeutic baths (balneotherapy). Sauna treat-ments, brushing the skin, and beating it with birch twigs are examplesof other therapies that stimulate peripheral circulation.


The Embryological Development of the Circulatory

System and Heart

Which comes first in embryology—the relatively open or the moreclosed system of circulation?1 In the early embryonic stages, circula-tion is totally open. Blood forms in some areas even before blood ves-sels exist. Human embryos begin producing blood in the beginningof the third week of gestation, which is very early compared to non-human primates (such as monkeys), although the anthropoid apes,our closest primate relatives, begin producing blood nearly as early.Blood begins forming when some cells differentiate into hemoangio-blasts that give rise to two main types of cells—erythroblasts (the firstred corpuscles) and angioblasts, which will later make up the vesselwalls. Hence, vessel walls arise from the same cells that also form theblood itself. It is important to note that the body does not behave likea plumber, first connecting the water pipes in a house and then turn-ing the water on. To the contrary, when the first blood-like liquid,which consists of hemoangioblasts and lymph cells secreted by thesurrounding tissue, appears in the extra-embryonic stalk, the yolk sacand the chorion, it simply trickles through gaps in the tissues (seeFigure 1). (The chorion is the outermost covering formed by theembryo itself; it later grows villi and develops into the fetal portion ofthe placenta.) Thus the first minute trickles of blood appear outsidewhat will become the body. This blood does not pulse but moves at asteady pace, although its direction is not predetermined and appearsarbitrary. Preferred channels develop only very gradually as bloodcells are deposited along the edges and eventually merge into thebeginnings of vessel walls. Of course we must not imagine that thefirst embryonic blood resembles that of a newborn, much less that ofa child or an adult. Embryonic development alone spans three gener-ations of erythrocytes (the megaloblastic, hepatolienal, and medullarphases of Kahle, et al. [6], see Figure 2). Once hemoglobin hasformed, however, we are justified in calling this fluid “blood.”

1. See also the chapter by M. Woernle in this book.


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When blood vessels first start to form, the heart does not yet exist.The heart also originates in the extraembryonic mesoderm between theamniotic cavity and the yolk sac in front of the later head (see Figure 3).It has the form of a little vesicle. The vesicle grows and becomes thepericardium and the myocardium (heart muscle). The vesicle descendsdownward in front of the face and throat into the upper and finally thelower chest (see Figure 4). The inner epithelium of the heart, theendocardium, arises out of many minute bilateral blood islands that

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merge into one main vessel. This vessel soon begins to bulge as the flowof blood intensifies. This bulge in the main vessel meets with the myo-cardium and together they form the basis of the heart. Hence, earlyblood flow stimulates the development of the heart. The heart therebysoon shifts to an asymmetrical position. The intricate twists and curvesof the cardiac loop develop, and dividing walls form and dissolve incomplex processes that eventually result in the four-chambered organ.

The early main vessel’s muscle fibers become contractile on aboutthe twenty-second day of development. The blood, which formerlytrickled through the heart and vessels at a steady rate, begins to movein pulses in the vessels that lead the blood out of the heart. Venousblood never pulses as strongly as arterial blood. It continues to flow ateven speeds, as all blood did originally. Its movement becomes slightlyrhythmic only where the pulsing of adjacent arteries influences it.

The Character of Venous and Arterial Blood

But what are the vital functions of venous circulation? Conventionalbiology has long perpetuated the erroneous belief that venous blood is“used up” and loaded with wastes, while arterial blood is the good,beneficial blood. Carbon dioxide, in particular, is considered a wasteproduct. Fortunately for us, however, not all of the carbon dioxide inour bodies is exhaled. Significant amounts remain, even in arterial

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blood. We could not survive for even a minute without enough carbondioxide in our blood, including arterial blood. Why not? The pH valueof blood is very specific. Whenever hydrochloric acid is secreted by thegastric mucosa or alkaline digestive juices by the duodenum, the com-plementary (OH)- or H+ ions enter the blood, where they couldcause excessive acidity or alkalinity if they were allowed to remain.That this does not happen is due in large part to bicarbonate buffer-ing, a major factor in the blood’s highly complex buffering system.We exhale only the excess carbon dioxide because we could not livewithout some of it in our blood. In actual fact, carbon dioxide playsan essential positive role in our circulatory system.

We have already heard that the original embryonic blood movesat a constant rate—that is, it is venous in character. Remarkably, thesame is true of gaseous metabolism, since early embryonic develop-ment takes place largely under oxygen-poor conditions. Fetal blooddoes not begin to be oxygenated until a functional placenta devel-ops, and even then complete oxygenation is avoided during prenataldevelopment. The oxygen levels provided by the mother’s circulationvia the placenta are never as high as the levels that functioning lungsafter birth would supply. Furthermore, the semi-oxygenated bloodthat flows in through the umbilical cord mixes with venous blood ontwo separate occasions (see Figure 5). First it mixes with the blood ofthe inferior vena cava. This mixed blood then flows into the right sideof the heart but immediately passes through the foramen ovale in thecardiac septum into the left side and then into the aorta, where itagain combines with venous blood, namely, the blood of the superiorvena cava, which enters the aorta from the right ventricle via Botallo’sduct (ductus arteriosus). Fetal placental blood reaches the developingbody only after this repeated mixing has occurred. Hence, venousblood is constantly mingling with arterial blood, and the most signifi-cant growth and development that the body ever undergoes occurs inthis strongly venous environment.

Comparative embryology sheds more light on the significance ofvenous blood [10]. It is astounding that no bleeding occurs when a cowgives birth normally. Although the bovine chorion (the outer coveringof the fetus) does develop fine villi, they never break down themother’s mucous membranes all the way to the blood vessels, as is the


case in humans. In cattle especially, but also in other ruminants, fetaltissue never destroys any maternal tissue, and oxygen and carbon diox-ide are exchanged across multiple intervening layers of cells. Oxygentransport is considerably more difficult under these circumstances.

In its very early stages, the forerunner to the human placenta, thetrophoblast, is similar to that of a cow, but in later stages it undergoes astep-by-step metamorphosis into the hemochorial placenta, whose villiactually breach maternal blood vessels and draw oxygen, blood sugar,and other needed substances directly from the mother’s blood. As a

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result, a normal human birth does involve some brief hemorrhagingwhen the placenta or afterbirth is expelled.

The embryos of certain other mammals tap the mother’s oxygensupply and breach the maternal tissue layers already in the very earlystages of placental development. These embryos are optimally sup-plied with nutrients and oxygen, and their circulation is oxygenated ata very early stage. Which mammals are these? They are the rodents—mice, rats, hamsters, squirrels, marmots, and so on. These are animalsthat remain small and also do not grow very large in utero. In contrast,animals like cattle, buffaloes, giraffes, and hippopotami all have tobuild up huge bodies. The fetal development of these huge bodiesoccurs in an extremely venous environment, they postpone oxygen-ation even beyond the time when it occurs in human fetal develop-ment. Evidently venous blood possesses quite remarkable properties.

Human blood is two-thirds venous by volume and only one-thirdarterial. This preponderance of venous blood suggests that thevenous environment must play an especially important role in thehuman body. In most invertebrates, the oxygen-carrying blood pig-ment is either chlorocruorin or hemocyanin and the circulatory fluidis either colorless or has greenish or bluish tints. Some invertebrates,however, do have true hemoglobin in their blood. These include theEuropean fresh water snail (Planorbis), some marine ribbon bootlaceworms (class: Nemertini), many annelids or segmented worms (Pecti-naria, Arenicola, Lumbricus, Tubifex, and Hirudo), and the crustaceanBranchipus schafferi. Of the insects, only the larvae of the non-bitingmidges (Chironomidae) have blood that contains hemoglobin. Onclose inspection, the larvae of various Chironomus species, also called“bloodworms,” reveal a morphological series. Species of larvae thatlive on the water’s surface have no hemoglobin, and their internaltracheal system takes in oxygen directly from the air. In larvae thatlive in deeper water, the tracheal system that is closed to the outsideabsorbs oxygen from the water and passes it on to the blood, whichcontains low levels of hemoglobin. Chironomus gregarius larvae, bot-tom-dwellers that live in oxygen-poor mud, have the most hemoglo-bin in their blood and accomplish gaseous exchange without the helpof their tracheal system, which has almost atrophied [8]. We humansalso produce more hemoglobin when we breathe high mountain air,


which contains less oxygen. Thus red pigment in the blood is an indica-tor or expression of the need for oxygen in the interior of the organism.

In the adult human body, some organs are better supplied with arte-rial blood than others are. The brain and the liver lie at opposite endsof this spectrum. The liver, which receives relatively little arterial blood,receives the most venous blood of all the organs. The hepatic portalvein that delivers blood to the liver is one of the largest veins in theabdominal cavity. It collects blood from the intestines, spleen, stomach,pancreas, and neighboring organs and sends it to the liver. The hepaticportal vein is the only vein in the human body capable of forming newcapillaries—an ability normally restricted to arteries. As a result, theliver contains a second, purely venous network of capillaries in additionto the capillary system of the liver artery. This venous environment isthe center of bodily nutrition, physiological regeneration and anabo-lism. Apparently, protein synthesis and countless other processes (suchas bile and glycogen production, urea synthesis, detoxification, etc.)need to take place in a predominantly venous environment.

In contrast, the brain is the organ that degenerates most quicklywhen its supply of arterial blood is interrupted. When an artery in anarm or leg is injured, a tourniquet can remain in place for up to anhour, although to avoid permanent damage the injury must be surgi-cally repaired within two hours. It is inconceivable, however, that thebrain’s blood supply could be cut off for that length of time, whichshows how heavily the brain depends on the constant supply of bloodsugar and oxygen that its arteries provide. The brain, the organ leastable to regenerate, suffers irreversible damage after only three min-utes of complete oxygen deprivation. Each of these two diametricallyopposed organs is also related to unique psychologicalcharacteristics—the brain is the organ of consciousness and the liverfunctions on a deeply unconscious level—that are supported by arte-rial and venous blood, respectively, in very different ways.

Given everything we know about these differences, it is no longerappropriate to place value judgments on the two kinds of blood, declar-ing one better and more important than the other. Both kinds of bloodplay important roles in the circulatory system. It is simply a fact thatorganisms are always undergoing simultaneous breakdown andrenewal. Breakdown of organic substances occurs with the help of the


oxygen supplied by arterial blood. Of course some renewal also takesplace where the arteries supply nourishment to the organs, but thepotential for renewal is greatest in areas of heavy venous supply—in thevenules of the intestines, for example. The venous environment so cru-cial to the embryo during its most explosive growth is no less essentialin maturity. We begin to have an inkling of what the ancients meant bycalling the content of the veins “pneuma.” In the veins, much morethan areas of heavy arterialization, blood is the source of life.

Heart Evolution

Comparative vertebrate anatomy reveals that a true heart is presentalready in fish.2 The fish heart is an exclusively venous organ. Fromthe heart, the blood moves toward the head and is oxygenated onlywhen it reaches the gills, after which, instead of flowing directly backto the heart, it flows through the rest of the fish’s body. Especially atthis early stage of its evolution, the heart is a central collecting organfor the venous branch of circulation. This is also true of the larvalstages of amphibians, such as tadpoles and newt larvae. Most adultamphibians have lungs, enabling them to live on land. Increasing arte-rialization of the blood begins in the lungs. Blood vessels then bringthis arterialized blood from the lungs back to the heart. But in all adultamphibians and most reptiles, this arterialized blood mixes withvenous blood in the heart. In frogs and lizards, for example, there isan open foramen in the septum between the ventricles.

The crocodiles are the first animals with a closed cardiac septum(see Figure 6). The two kinds of blood emerge separately from thevenous and arterial sides of the heart, but the foramen of Panizzaallows them to mix on leaving the heart [15]. In addition, the bloodthat flows through the large reptilian aortic arches (the arterial archon the right and the venous on the left side) mingles again through ananastomosis below the heart. Thus, although it has separate heartchambers, the crocodile’s body mixes the two kinds of blood again out-side the heart; that is, the blood does not remain fully oxygenated.

2. See also the chapter by C. Liesche in this book.


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Birds, which are warm-blooded creatures, are the first animals inwhich venous and arterial circulation become completely separate, asthey normally are in mammals and humans, at least after birth. When anewborn inhales for the first time, blood is squeezed out of the lungs,which until then resembled a blood-soaked sponge, and the resultingrush of blood back to the heart permanently closes the last openingbetween the atria (i.e., between the arterial and venous bloodstreams).

To sum up, in the early stages of both individual embryonic devel-opment and vertebrate evolution, the heart is purely venous. It arteri-alizes step by step, ultimately achieving complete separation of the two

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kinds of blood. It is interesting to note that complete separationoccurs first in bird species with their relatively rich soul life. Birdsong,although by no means as advanced as human speech, is nonethelessrichly expressive, and the intimacy and closeness of birds’ relation-ships to their young occur only among warm-blooded animals. Whenyoung crocodiles hatch, they immediately head for the water andwould never recognize their mother if they happened to meet her onthe way. She, too, would not recognize them. Guarding her eggs anddigging up the young after they hatched were completely unemotionaland impersonal tasks. Once she has performed these services, hermaternal instincts are immediately transformed into feeding instincts,in whose grips she would eat even her own young without hesitation.In contrast, mother birds are intimately attached to their offspring,and mammals still more so—especially humans, for whom the child-rearing and nurturing period is greatly extended by their offspring’sslowness to mature. We see, therefore, that increasing arterialization ofthe blood is accompanied by increasingly rich and flexible behavior.Just as a venous environment is important for organic growth, arterial-ization of the body supports oxidative breakdown processes, whichconstitute the physiological basis of a complex psychology.

Models of the Heart in Comparison to the Heart Itself

Numerous models of the heart and its function exist today.Researchers, hoping to make heart transplantation unnecessary, con-tinue to work on artificial hearts, although they encounter consider-able difficulties, primarily due to the fact that wherever bloodencounters any unfamiliar object or obstacle, it immediately begins toclot, causing embolisms or thromboses. Surgeons first tried using plas-tic to replace blood vessel walls (in repairing an irreparably damagedsection of the aorta, for example), but when they eventually realizedthat the blood will not tolerate the intrusion of even the most inertartificial substance, they discovered an interesting solution. When theysubstituted a porous tube of nylon or Teflon, the blood began filling inthe pores in the tube as soon as it was allowed to flow through. Thehematoma that formed as blood thickened along the edges gradually


made the tube impermeable. With continued flow, a new, living inte-rior wall was gradually built up. Slowly the various layers of the aortadeveloped, using the porous plastic implant as a base [9]. The bloodhas a lifelong ability to regenerate its vessels in this way. The heartitself, however, cannot regenerate in this manner.

The different models or concepts of cardiac function view the heartas a pump. Models typically grasp only a part of reality, which is why wecall them “models.” Nonetheless, they do describe some aspects of howthe heart functions. Rudolf Steiner discusses a conceptual model devel-oped by an Austrian physician named Karl Schmidt (1857-1915), whoworked in the province of North Styria. Schmidt would have been for-gotten long ago if Rudolf Steiner had not called attention to him in lec-tures given in 1910 and 1920 [12, 13]. Schmidt believed that thegenerally accepted concept of the heart as a pump was inadequate andproposed in its place the model of the hydraulic ram or water ram, adevice that needs no outside energy source but pumps water to a higherlevel using only the energy of the stream itself [11]. In some rural areas,you can still see these little flow-driven waterworks operating at no cost.A hydraulic ram uses the energy of flowing water to raise part of thatwater against the force of gravity to an elevation higher than the source.Similarly, flowing blood provides the energy—here more chemicallythan physically—the heart needs to keep circulation going, althoughthe heart, unlike the hydraulic ram, actively contracts and expands.

In a hydraulic ram, water flows from the source through a drivepipe, escaping through an escape valve until sufficient pressure buildsup to suddenly close the escape valve (see also the description and dia-gram in Appendix B). Water then surges through the interior dis-charge valve into an air chamber, compressing air trapped in thechamber. When the pressure of the inflowing water reaches equilib-rium with the trapped air, it rebounds, causing the discharge valve toclose. The water then escapes from the air chamber through an exitport and up a delivery pipe to its destination. The closing of the dis-charge valve causes a slight vacuum, allowing the overflow valve toopen again, initiating a new cycle. The name “ram” comes from theforceful rebound of the water. According to Schmidt’s interpretation,the function of the cardiac valves is to produce a rebound that makesthe upward flow of blood possible [11].


Previously, the cardiac valves had been thought to serve no otherpurpose than to prevent the backflow of blood, but as Liebau demon-strated in 1954, this argument is by no means convincing [7]. Liebaudeveloped a model of the circulatory system in which one-directionalflow is maintained without any flaps or valves. This model requiresonly an asymmetrically given impulse to the flow within in a circulartube with walls of varying thickness and therefore varying elasticity. Inthis model, flow is possible in one direction only, as anyone who triesthis experiment soon discovers.

The heart, however, does have valves (both atrioventricular andsemilunar valves), which raises the question of whether the hydraulicram principle or the Liebau principle is in effect there. In a personalcommunication, the physician and chronobiologist Günther Hilde-brandt (1924-1999) pointed out that both principles can be observedin cardiac activity. Any physical exertion or agitation makes the beat ofthe heart valve stronger and rebounding serves to gather energy forthe next action. During exertion, therefore, the heart leans toward thehydraulic ram model. During sleep, however, when cardiac activity ismore closely linked to regenerative (trophotropic) than to active(ergotropic) processes, it more nearly resembles the Liebau model inthat it does not necessarily depend on valve action—instead, the valvesare set in motion by the even, rhythmical flow of the blood. (This phe-nomenon is reminiscent of the hemodynamic creation of sail-like flapsin early embryonic stages. Such flaps develop wherever the blood flowsmore gently, producing areas of suction.)

In its earliest stages, the heart is completely valveless. With the awak-ening of day-consciousness and an increasingly outward-directed emo-tional life, damming-up functions and rebounding (which gathers andconcentrates flow energy) take center stage. When agitation prevents usfrom falling asleep at night, our strong heartbeat can disturb us. In con-trast, patients with valve disorders may have no trouble sleeping (or rest-ing during the day), but must avoid agitation and excessive activity.

The difference between nocturnal and diurnal cardiac activity mir-rors the difference between venous and arterial circulation. Arterialcirculation carries the pulsing blood; venous blood flows at a moreeven pace. As it alternates between nocturnal and diurnal rhythms,cardiac activity more closely resembles first one, then the other form


of circulation, yet its transitions are smooth and it is also always respon-sive to momentary bodily and emotional needs. It gives us the open-ness to adapt to changing soul-body interactions, whether we are calm(in which case regenerative processes predominate) or stressing ourcirculation by running to catch a train. The conceptual models pro-vided by physics can portray only the extremes; the living reality liesbetween them.

Spatial Attributes of the Heart

The terms we use to describe the heart (right and left ventricles orright and left atria separated by septa, etc.) imply that it is symmetrical,but the reality is not that simple (see also Appendix A). The morphol-ogy of the heart is complex because it is somewhat, but not strictly bilat-erally, symmetrical. In relation to the symmetry of the body as a whole,the location of the heart (almost, but not quite, in the center of thebody) is less asymmetrical than that of the spleen or many otherabdominal organs. Similarly, the structure of the heart itself is neithersymmetrical nor purely asymmetrical. This is an essential phenomenon.

Observation of the organs most closely related to our waking con-sciousness reveals that they are all bilaterally symmetrical. The func-tions of our sense organs, central nervous system, skeleton, andskeletal muscles can all be influenced directly by our waking conscious-ness. Because of these symmetrical organs, the human body lookstotally symmetrical from outside. Its internal organs, however—andespecially those in the abdominal cavity—are often asymmetrical. Thespleen lies on the far left, the stomach quite far to the left. The liver,gall bladder, and appendix are on the right side of the body, the pan-creas on the left. The convolutions of the intestines are also not sym-metrical.

The symmetry or asymmetry of organs corresponds to how we expe-rience their activity. Most symmetrical organs are subject to voluntaryinfluence, while asymmetrical organs are not. I can make a fist deliber-ately, but I cannot make bile flow into my duodenum. We would prob-ably cause serious problems for ourselves if we had to exert consciouscontrol over our unconscious bodily functions. Under normal circum-stances, it makes perfect sense that our metabolic organs, which are


totally responsible for regenerating the body, are always in a state ofunconscious sleep. When we awaken in the morning, we awaken onlypartially. Part of us—namely, our asymmetrical organs—is asleep dur-ing the day as well as at night. In contrast, our symmetrical organseither actively support day-consciousness or are at least more stronglyinfluenced by it than our asymmetrical organs are.

But does the heart belong to either of these two groups? The heartis almost centered in the chest, but its axis, as seen from both the sideand the front, does not coincide with the axis of the body’s externalsymmetry. The heart avoids strict symmetry yet without becoming com-pletely asymmetrical. This curious semi-symmetry, however, still doesnot describe the reality of the heart, which is always in motion andchanges shape constantly. In contraction (systole) and expansion(diastole), the heart’s axis oscillates between a more asymmetrical anda more symmetrical position relative to the chest. The heart’s dynamicmorphology mediates and creates harmony between these two poles.We must see the shape of the heart as more than coincidental andcomplicated. We must see it as a fascinating synthesis of the structuresof all other organs. It draws on all their shapes to become the mostuniversal of them all. Clearly, therefore, the heart is more than apump. The symmetry or asymmetry of a pump is irrelevant as long as itsets liquid in motion.

The morphology of the heart as a whole suggests that it does morethan merely fulfill a mechanical function. Once we acknowledge theconnection between symmetry and consciousness, common figures ofspeech involving the heart regain their original meaning. In everydayconversation, we usually use the word “heart” to refer to emotionsrather than to anatomy. We say that someone is “warm-hearted” or“cold-hearted,” “heartless” or “heartbroken.” In our hearts, we experi-ence by means of emotions that are neither fully conscious nor asdeeply unconscious as bile secretion, for example. Our heart senseswhat goes on in the intermediate state between sleeping and waking—that is, in dreaming. In our emotional life, we are always dreaming.The shape of the heart is related to this psychological middle realm inthe same way that the asymmetrical shapes of our intestines relate tothe unconsciousness of sleep and the orderly, symmetrical forms ofour sense organs to alert, fully conscious perception of the world


around us. Is this why our waking consciousness always strives for clearand orderly thinking and why dimly sensed threshold experiencescoming from the unconscious seem so much more chaotic to us? Is itwhy our feelings help us transcend the alternatives of strict lawfulnessand impulsive reactions? The whole body, not just the central nervoussystem, is the instrument of the soul.

Today this insight into the role of the heart is confirmed by observa-tions of heart transplant patients, although unfortunately a taboo per-sists against publishing reports on the psychological consequences ofheart transplantation. As one study states,

Heart transplant recipients overreact to problems of everyday life, which means that any latent psychological disorders they had before surgery may worsen, complicating their recovery signifi-cantly…. Therefore, Dr. Stuart Finch, professor of psychiatry at the University of Michigan, Ann Arbor, recommends that psychologi-cally imbalanced patients not receive heart transplants, since their chances of recovery are not very good. (16)

The head of the heart transplantation center in Hannover, Ger-many, stated in a television interview that they transplant only if thepatient lives in a stable marriage or relationship. The partner must beable to give psychological support during the whole time, otherwisethe prognosis for survival during the next five years is too uncertain.(For a recent exploration of heart transplants, see reference 1).

Body and soul interact in all organs, and their interaction is evidentin the organs’ morphology and degree of consciousness. When we arehappy or sad, frightened or ashamed, our circulation is affected imme-diately. It slows down or speeds up, sending blood to the periphery tomake us blush or concentrating it in central vessels and the heart tomake us pale. Of course we can study the influence of hormonal pro-cesses such as the release of adrenaline, but physical substrates alonenever explain the inner, emotional characteristics. Rudolf Virchow wasperfectly correct when he stated in the nineteenth century that he hadsearched the whole body with his scalpel without finding anythingresembling a soul, not even in the pineal gland, which Descartesbelieved to be the seat of the soul. In Virchow’s sense, the soul and its


properties cannot be discovered with a scalpel. Our relationship to ourfellow human beings, however, becomes problematic whenever weregard others as creatures that can be understood completely bymeans of the scalpel or the microscope. If that is all they are, then theyare indeed objects to be “manipulated” at will for their greater “happi-ness.” But any manipulation of human beings is inhumane. Today wecan all realize that we are beings, not objects, and that as such we arenot to be manipulated by the collective demands of the state or anyother institution but are capable of making our own decisions aboutour existence. Every generation has to come to this realization anew.

Rudolf Steiner’s Anthroposophy challenges us to observe, and toobserve not only in the material world but also in the world of soul andspirit. Each of us is active in soul, spirit, and body. Why, then, do weobserve only bodily processes? We must begin to observe what happenson the level of soul and spirit as well, not only in ourselves, but also inthose around us. If we do so, we will create new social, therapeutic, andeducational climates in which the world view of the natural sciences isnot only fully accepted where it is applicable (i.e., in exploring spatialand physical phenomena) but also expanded to include exploration ofthe soul and spiritual aspects of our world. These two forms of scienceneed not remain separate. They could supplement and corroborateeach other, especially in fields such as the study of the circulatory sys-tem and the morphology of the heart, as this brief discussion wasintended to demonstrate.

References

1. Bavastro, P. 1999. Herztransplantation—Eine kritische Betrachtung. InBavastro, P. and Kümmel, H.C. (eds.), Das Herz des Menschen. Stuttgart: Ver-lag Freies Geisteleben, pp. 267-293.

2. Harvey, W. 1628. Exercitatio anatomica de motu cordis et sanguinis in animali-bus. Frankfurt.

3. Hensel, H. 1978. Hämodynamik. 5. Rundbrief der Internationalen Vereinigungder Waldorfkindergärten e.V., pp. 14-16.

4. Jahn, J. (ed.) 1998. Geschichte der Biologie. Jena, Stuttgart, Lübeck, Ulm.5. Kraft, F., and A. Meyer-Abich. 1970. Grosse Naturwissenschaftler. Frankfurt

am Main.6. Kahle, Leonhart, and Platzer. 1973. DTV-Atlas der Anatomie, Band 2: Innere

Organe. Munich/Stuttgart: Deutscher Taschenbuchverlag.


7. Liebau, G. 1954. Über ein ventilloses Pumpprinzip. Die Naturwissenschaften41(14): 327.

8. Pause, J. 1919. Biologie und Physiologie der Larve von Chironomus gre-garius. Zoologische Jahrbücher 36: 337-452, especially 441 ff.

9. Schad, M. 1960. Alloplastischer Arterienersatz. Dissertation, University of Mar-burg.

10. Schad, W. 1977. Man and Mammals: Toward a Biology of Form. Garden City,New York: Waldorf Press, Adelphi University.

11. Schmidt, K. 1892. Über Herzstoss und Pulskurve. Wiener MedizinischeWochenschrift Nr.15.

12. Steiner, R. 1959. Menschengeist und Tiergeist, lecture of November 17,1910. In Antworten der Geisteswissenschaft auf die grossen Fragen des Daseins(GA 60). Dornach: Rudolf Steiner Verlag.

13. Steiner, R. 1999. Introducing Anthroposophical Medicine, Chapter 2 (Lecturefrom March 22, 1920). Hudson NY: Anthroposophic Press.

14. Vogler, P. 1972. Disziplinärer Methodenkontext und Menschenbild. InNeue Anthropologie, Band 1. Stuttgart: Deutscher Taschenbuch Verlag, pp. 3-21.

15. Wurmbach, H. 1968. Lehrbuch der Zoologie, 2nd ed. Stuttgart.16. No author noted. 1970. Persönlichkeitsveränderungen bei Transplanta-

tionen festgestellt. Universitas 25(8): 884.

5

P a t t e r n s i n t h e E v o l u t i o n o f t h e H e a r t a n d C i r c u l a t o r y

S y s t e m

C H R I S T I A N E L I E S C H E

IN THIS ESSAY we will discuss the characteristics of the cardiovascular sys-tems of different animal phyla and classes in relation to the humanbeing. This discussion will serve as a basis for understanding thehuman heart and circulatory system, as well as the steps involved in theevolution of these systems. We will also shed light on the circulatory sys-tem’s evolution by describing other organ systems. As we do so, it willbecome evident that progressive evolution through the various animalphyla leading up to the human being involves the successive emancipa-tion of seven organ systems from the constraints of the environment [3,7]. These are the sensory system, the central nervous system, the respi-ratory system, internal fluid regulation, thermoregulation, reproduc-tion and, finally, the musculoskeletal system.

Invertebrates achieve a high degree of specialization in their sensoryorgans. The fish, which belong to the vertebrates, have a central ner-vous system whose function is to supervise and coordinate the activityof the entire nervous system. Amphibians internalize the respiratory

Pat t e rns in the Evolut ion o f the Hear t and Circulatory Sys t em 9 9

system through the development of lungs, thus freeing themselves, toa degree, from life in the water. Reptiles have horny, scaly skin, whichallows them to control their internal fluid balance independent oftheir environment. In birds, warm-bloodedness (endothermy) consti-tutes a further step in emancipation from environmental conditions.The mammals internalize the reproductive process, but their muscu-loskeletal systems are still determined by their respective environ-ments. This final step in emancipation is reserved for human beings.

Insects

Insects, the most highly evolved invertebrates, typically have com-plex sensory organs. Their compound eyes, which are very finelyadapted to the physical laws of light, enable them to track movingobjects, sense polarized light, and distinguish colors. The fine hairsthat cover an insect’s body are sensitive to touch and to changes in spa-tial orientation, and its delicate antennae are not only highly sensitivetactile organs but also serve to perceive odors and sounds. Organs oftaste are located primarily in and around the mouth but may also befound on the feet. Inasmuch as its life is governed by external stimuli,the entire insect body is a sense organ. Its fixed patterns of behaviorare closely linked to the daily and yearly course of the sun. The insecthas no overriding central nervous system. A ganglion formed by thefusion of the two ventral nerve strands regulates the functions of eachsegment of its body. Respiration in insects is also not associated with aspecific organ. Instead, air flows through the entire insect by means ofa finely branched system of tubes called trachea. Similarly, warmth reg-ulation, reproduction, and movement in insects are also environmen-tally determined.

What type of circulatory system can we expect to find in suchorganisms? Instead of a closed circulatory system, insects have a singlepulsating dorsal vessel that is open at one end, near the head, andclosed at the rear (Figure 1). The blood flows into this pulsating vesselfrom the sides, through narrow ostia, and then moves toward thehead. On its return path, it flows freely around the tissues of the tho-racic cavity to the abdomen, where it is once again sucked into the dor-sal vessel. In insects, flow velocity (0.5-20 mm/sec) and blood pressure

1 0 0 T H E D Y N A M I C H E A R T A N D C I R C U L A T I O N

(5-10 mm Hg) are both very low. Because its colorless corpuscles cannotbind oxygen, insect blood (hemolymph) functions only to distributenutrients and is therefore primarily an organ of anabolic metabolism.

Fig.1: The circulatory system in insects: (a) diagram of blood circulation; (b) cross-section ofthe pulsating dorsal vessel, and the muscle fibers of the dorsal diaphragm viewed from above.1: wings; 2: pulsating dorsal vessel with ostia (openings); 3: ostia (openings); 4: dorsal diaphragm;5: ventral diaphragm.

The sign of a well-functioning sensory apparatus is its outstandingability to make contact with the surrounding world. As such, its organsare open to the environment. Analogously, blood circulation in insectsis also “open,” and no heart has evolved.

Fish

The evolution of vertebrates begins with the fish. Fish have evolvedfurther than insects by developing a central nervous system thatincludes a brain and a spinal cord, which are protected by the skulland vertebral column respectively. The vertebral column is the mainpart of the fish’s endoskeleton, which mainly stabilizes the trunk andtail fin. In contrast, insects develop only an exoskeleton, which coversthe entire body.

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Pat t e rns in the Evolut ion o f the Hear t and Circulatory Sys t em 1 0 1

As is evident from all their other organ systems, fish are totallyadapted to their aquatic habitat. Hence, respiration takes place pas-sively in the gills. As the animal moves forward with its mouth open, astream of water bathes the gills, where oxygen is absorbed and carbondioxide eliminated. Fluid balance, thermoregulation, reproduction,and limb development in fish are similarly dependent on environmen-tal forces.

How is the cardiovascular system organized in fish? Their blood cir-culation, in contrast to that of insects, is closed; the blood and its cellu-lar components flow through a system of vessels instead of streamingfreely through the body cavity. Furthermore, the specialized red bloodcells that fish species have evolved are capable of binding oxygen andcarbon dioxide. This self-containment of the vascular system isreflected in the development of a heart of sorts, a ventrally locatedtube-like organ that is divided into a single atrium and a single ventri-cle. In more evolved fish species, the heart is twisted into an s-shape sothat the atrium lies above the ventricle (Figure 2). Through this curva-ture, the heart increasingly becomes a more self-contained organ.

Figure 2: The heart of fish: (a) diagram of the heart of primitive fish; (b) diagram of the heartand gills of bony fish. Black = venous blood; white = arterial blood;1: vein coming from thebody; 2: sinus venosus; 3: atrium; 4: ventricle; 5: bulb of the heart; 6: ventral aorta; 7: gills; 8: dorsal aorta.

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The venous blood flowing in the large vessels collects in the sinusvenosus before entering the atrium, from where it moves into the ventri-cle. The ventricle is more muscular than the atrium and actively com-presses the blood before it flows into the bulb of the heart. The bulb ofthe heart contains several pairs of valves to prevent the backflow of bloodinto the ventricle. The venous blood then flows through the single ven-tral artery into the vascular network of the gills, where it is oxygenated.Most of this freshly oxygenated blood flows into the two dorsal (carotid)arteries that lead to the head, but another part turns back into the singledorsal aorta, which leads to the tail and supplies the capillary beds of theabdominal organs. This arrangement allows for only a primitive type ofseparation of venous and arterial blood by placing arterial and venousblood into a sequential, but not yet parallel function. As a consequence,the heart is supplied exclusively with nutrient-rich venous blood.

Although the development of the central nervous system in fishmarks a further step toward physiological freedom within the aquaticenvironment, they are still dependent on external influences withrespect to their other organ systems. Fish represent early stages in theevolution and differentiation of the vertebrate cardiovascular system.

Amphibians

Amphibians, the next class of vertebrates, make the transition fromaquatic habitats to life on land. Because amphibians have no dia-phragm and poorly developed ribs, they can only fill their lungs byswallowing air. Respiration is thus driven by the muscle activity of thethroat. The oxygen-rich air they inhale does not enter the lungsdirectly, however, but first mixes with exhaled, oxygen-poor air in thethroat as it enters the lungs. Yet in amphibians, the chest with the lungas its central organ is more clearly distinguished from the head than itis in fish, which have no defined “neck” at all. The differentiation of aneck region in amphibians is the first step toward freeing up the shoul-der girdle to serve the development of the forelimbs.

Amphibians still depend on respiration through the skin to meet asignificant portion of their oxygen needs. Their thin, moist, permeableskin with its many glands also restricts them to damp habitats becausethey have not yet internalized the process of fluid regulation. Their


ability to move also depends on an environmental factor, namely, tem-perature, and they spend the cold winter months in a dormant state.Their reproduction is still exclusively dependent on water; as in fish, fer-tilization occurs outside the body. Inside its gelatinous capsule, theamphibian embryo develops into a larva that initially still has gills andlacks limbs. The transition to life on land occurs only after metamorpho-sis, when the tadpole’s lungs have become functional. The limbs ofamphibian species are also adapted to their moist or aquatic habitats.

Fig. 3: Diagram of the heart and lungs in amphibians. Black = venous blood; white = arterialblood; light dots = mixed arterial; dark dots = mixed venous; 1: vena cutanea (the vessel carry-ing oxygenated blood from the skin); 2: anterior vena cava; 3: pulmonary vein; 4: posterior car-dinal veins; 5: posterior vena cava; 6: left atrium; 7: ventricle; 8: arterial trunk; 9: carotid artery;10: dorsal artery; 11: pulmonary artery; 12: subclavian artery (the artery serving an extrem-ity); 13: lung.

In the amphibian cardiovascular system, the heart and lungs lieside by side in the chest cavity instead of one behind the other in thehead, as is the case in fish. In contrast to the fish, the venous and arte-rial blood streams meet in the heart (see Figure 3). In amphibians, aseptum divides the atrium (which is still a single chamber in fish) intoright and left halves. Venous blood from the body and arterial bloodfrom cutaneous respiration flow through the sinus venosus into theright atrium, while arterial blood from the lungs flows directly into theleft atrium. In the ventricle, these two types of blood meet but mingleonly to a limited extent, although there is no septum separating the

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blood flows (see Figure 4). Venous blood collects in the right half ofthe chamber, while arterial blood from the left atrium accumulates inthe left half. This functional separation is maintained during ejectionbecause the two halves of the chamber contract sequentially, first theright half and then the left. A spiral-shaped endothelial fold guides thevenous blood from the right half of the chamber into the right side ofthe arterial trunk, which leads to the pulmonary arteries. As the lefthalf of the ventricle and the arterial trunk contract, the mixed bloodflows to the left of the spiral fold to the arteries leading to the lowerbody. Through morphological separation of venous and arterial bloodin the atria and functional separation in the ventricle, the lungs ofamphibians are supplied with pure venous blood, the head with arte-rial blood, and the intestines and limbs with mixed blood.

Fig.4: Diagram of the frog heart. 1: pulmonary vein; 2: vena cutanea; 3: mouth of the sinusvenosus; 4: left atrium; 5: muscular wall of the ventricle; 6: posterior vena cava; 7: arterialtrunk with spiral endothelial fold; 8: right atrium; 9: anterior vena cava; 10: pulmonary arteries;11: right aortic arch; 12: carotid arteries; 13: anterior vena cava; 14: left aortic arch.

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The internalization of the lungs as the central organ of respirationis accompanied by increasing arterialization of the circulatory systemas it approaches the heart. Arterial blood flows directly from the lungsback to the heart. Inasmuch as amphibians are still partially depen-dent on cutaneous respiration, their circulation remains linked to theouter world.

Reptiles

Reptiles are the first class of vertebrates to fully emancipate them-selves from aquatic habitats. Their horny, scaly skin, which does notpermit free exchange of fluids with the environment, greatly assiststheir system of fluid regulation in becoming self-contained. As a result,reptiles can live in extreme habitats such as deserts. Their aggressive-ness and their quick, agile movements further distinguish them fromthe rather sluggish amphibians. Reptile respiration takes place exclu-sively in the lungs. The surface area of their pulmonary epithelium isgreater than that of amphibians, increasing oxygen absorption.

Reptiles have not developed warm-bloodedness; their body tempera-ture varies with that of their surroundings. Their reproduction, too, isstill dependent on environmental factors. Most reptiles lay eggs. But fer-tilization is internal and, in contrast to the amphibian embryo, the rep-tile embryo is enclosed in a calcareous or parchment-like shell. Theamnion, a membrane that lines the shell and provides an additionallayer of protection against drying out, can be viewed as one of the mostimportant evolutionary innovations leading to the internalization andemancipation of fluid regulation in reptiles. Although reptiles no longerundergo the fully exposed larval stage typical of amphibians, reptile eggswith their parchment-like, water-permeable shells take up large amountsof water from the environment and therefore still require a moist envi-ronment. Most oviparous reptiles bury their eggs in the ground.

The limbs of different reptiles are extremely well adapted to theirrespective habitats. Turtles—sluggish animals in which metabolic pro-cesses preponderate—have evolved legs suited to digging and swim-ming. Snakes are aggressive animals in which the sensory-nervoussystem dominates. Although their limbs have receded, their tubularmuscles allow them to move very quickly. The crocodiles occupy an


intermediate position. Their hind legs are webbed and their oar-liketails propel them through the water.

What new features do we find in the reptilian cardiovascular sys-tem? In reptiles, venous and arterial blood is separated by a septum inthe ventricle of the heart. This evolutionary stage is most advanced incrocodiles, in which a septum divides the ventricle into left and righthalves. In snakes, lizards, and turtles, this septum is still incompletelydeveloped. At this evolutionary stage, the heart is divided into fourchambers for the first time, and the separation of venous and arterialblood occurs on a morphological level rather than functionally, as isstill the case in amphibians. The heart is fully incorporated into thecirculatory system as its central organ (Figure 5).

Fig. 5: Diagram of circulation in the crocodile. Black = venous; white = arterial; light dots =mixed arterial; dark dots = mixed venous; 1: left aortic arch; 2: foramen of Panizza; 3: pulmo-nary vein; 4: left atrium; 5: left ventricle; 6: interventricular septum; 7: celiac artery; 8: dorsalartery; 9: right ventricle; 10: right atrium; 11: posterior vena cava; 12: anterior vena cava;13: pulmonary arteries; 14: right aortic arch; 15: internal carotid artery; 16: external carotidartery; 17: subclavian artery.

Oxygenated blood from the lungs enters the left atrium. From theleft ventricle, it flows into the right aortic arch and then branches off

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into the arteries leading to the head and extremities. Oxygen-poorvenous blood from the body flows through the right atrium to theright ventricle and then to the lungs. Also emerging from the rightventricle is the left aortic arch, which supplies the intestines. At thebase of this arch, an opening called the foramen of Panizza allowssome arterial blood from the left ventricle to mingle with the venousblood in the left aortic arch. Consequently, the head and forelimbsreceive pure arterial blood, while the intestines are supplied with pri-marily venous blood from the right side of the heart, mingled withsome arterial blood that enters through the foramen of Panizza fromthe left side of the heart. The hind limbs are supplied with primarilyarterial blood from the left side of the heart, but there is still somemixing of venous and arterial blood through an anastomosis betweenthe aortic arches below the heart. Thus in reptiles the two types ofblood are completely separated only in the heart itself, but incom-pletely separated in the vascular system supplying the intestines andthe posterior extremities. In crocodiles and aquatic turtles this isthought to help in prolonged diving by restricting maximal oxygensupply exclusively to the head and forelimbs. By internalizing fluid reg-ulation and developing the interventricular septum, reptiles takeanother step toward emancipation from the environment.

Birds

Warm-bloodedness (homeothermy) is one of the chief characteris-tics distinguishing birds from reptiles. Even in winter, birds maintain aconstant body temperature, which can be as high as 41o C in smallbirds. Constant movement and the absence of winter dormancy is typi-cal of birds, as is a high metabolic rate. A consequence of this fastmetabolism is the disproportionately large avian liver, which has sev-eral portal veins and is needed for the generally large demand for car-bohydrates during the highly increased locomotor activity of birds,especially when migrating. Birds live in all types of habitats, fromdeserts, mountains, swamps, and tropical forests to the polar icecaps,and some virtually never touch the ground thus demonstrating theiremancipation from the environment that is to a large extent due totheir ability to keep a constant high body temperature.


In contrast, avian reproduction is still relatively dependent on envi-ronmental factors. Fertilization is internal, but embryonic developmenttakes place in the egg, outside the mother’s body. In comparison to rep-tile embryos, however, unhatched birds are far more protected fromenvironmental influences by their harder calcareous shells, by the warm-ing brood patches on their parents’ breasts, and by the structure of thenest itself. One or both parents protect the eggs. Postnatally, parentalcare is the rule rather than the exception among birds. The parentsguard, feed, and interact in various ways with their offspring. In manybird species highly differentiated social interactions are carried into andelaborated in adulthood and are a central characteristic of bird life.

Fig. 6: Diagram of circulation in birds. Black = venous, white = arterial; 1: pulmonary vein;2: left atrium; 3: left ventricle; 4: interventricular septum; 5: right ventricle; 6: right atrium;7: posterior vena cava; 8: anterior vena cava; 9: pulmonary arteries; 10: subclavian artery;11: external carotid artery: 12: internal carotid artery; 13: right aortic arch; 14: dorsal aorta.

Avian warm-bloodedness is accompanied by the complete separa-tion of venous and arterial blood in the heart (Figure 6). Venous bloodfrom the body flows through the right atrium into the right ventricle

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and then to the lungs. Oxygenated blood from the lungs enters theleft ventricle via the left atrium and then moves out into the bodythrough the right aortic arch. (During the embryonic period, the leftaortic arch atrophies and the symmetrical arrangement of the aorticarches is lost.) Venous and arterial blood is separated not only in theheart but also in the blood vessels. The head, the extremities, and eventhe intestines are supplied with pure arterial blood. This increase inthe relative volume of arterial blood is reflected in the stronger devel-opment of the muscles in the left half of the avian heart as comparedto the right. The increased demands on circulation in birds are alsoreflected in the spiral muscle fibers of the heart, a fast heart rate, highblood pressure, the development of anastomoses that permit ther-moregulation via the bloodstream, and a much higher number of redblood cells than in reptiles. Thus the higher evolutionary level repre-sented by avian species is characterized not only by internalized ther-moregulation but also by a more differentiated arterial system.Internal warmth regulation correlates with increasingly rich psycho-logical activity as expressed in song, in intensive parenting, and insocial behavior in general.

Mammals

While embryonic development takes place externally in birds, inhigher (eutherian) mammals it is fully incorporated into the mother’sbody. This places new demands on circulation because the circulatorysystems of mother and infant must be linked via the placenta, whichevolves as the organ mediating between them. In this way, reproduc-tion becomes completely independent of the external environmentand takes place within the protection of the mother’s body. Possiblymore than any other single evolutionary innovation, this additionalprotection allows eutherian mammals to achieve a further level of dif-ferentiation.

With the increasing internalization of pre-natal development andthe concomitant stronger relation between mother and offspring,(both pre- and postnatally) a greater basis for psychological emancipa-tion from the environment is provided. This is expressed in the largeand varied learning capacity of mammals.


In what respect are mammals still physiologically bound to theirenvironment? In their skeletal system, and especially in their limbs,mammals are totally adapted to specific habitats. Most mammalianlimbs are highly specialized to serve specific functions. For example, amole’s paws are adapted to burrowing through soil, a bat’s wings to fly-ing, and a horse’s legs to running and jumping grassy plains. The pro-portions of mammalian limbs reveal that they adapt to environmentalconditions. Anatomical analysis of mammalian limbs reveals that ingeneral the segments closer to the body are foreshortened, whileperipheral (distal) segments are increasingly elongated [7].

Fig. 7: Diagram of circulation in mammals. Black = venous; white = arterial; 1: pulmonary vein;2: left atrium; 3: left ventricle; 4: interventricular septum; 5: right ventricle; 6: right atrium;7: posterior vena cava; 8: anterior vena cava; 9: pulmonary arteries; 10: right subclavian artery;11: internal carotid artery; 12: external carotid artery; 13: left subclavian artery; 14: left aorticarch; 15: dorsal aorta.

Which unique characteristics distinguish the cardiovascular systemof mammals from that of birds? In most mammals, the heart is dis-placed from the central location it typically occupies in birds and isshifted somewhat to the left. Furthermore, the left aortic arch is com-pletely developed in most mammals and supplies the upper left and

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two lower extremities as well as the internal organs of the torso (Figure7). In contrast, the right aortic arch is less developed and leads only tothe right forelimb via the subclavian artery. The distinctive spiral formof the cardiac muscle fibers is still more pronounced in mammals thanin birds. As a result, eutherian mammals--with the exception of theirlimb system—have progressively developed physiologically to allowgreater freedom within their environment.

The Human Being

Only human beings raise their skeletons into the upright position,giving the upper limbs and head greater freedom. This phenomenonis correlated with the reversal of typical mammalian proportions in thelimb bones. In humans, the bones closer to the trunk are elongatedwhile the bones that contact the surrounding world are foreshortened.Humans can guide their actions inside outward. Because human fore-limbs with their unspecialized hands are relieved of the burden of sup-porting the body, human beings can direct the activity of their handsfrom within with an additional increase of freedom and precision. Instanding and walking, the human body balances on the straightenedlegs and arched feet that are typical of humans alone. The headremains at rest while the body below moves. The limb-like parts of thehead—that is, the jaws—serve the more internalized function ofspeech. Consequently, human beings are distinguished from animalsby their upright gait, by their ability to speak, and by the ability tothink independently of sense perception.

The human cardiovascular system is still more differentiated thanthat of mammals. For example, the spiral structure of cardiac musclefibers is even more pronounced than in mammals and birds. If we exam-ine the many variations that appear in mammals, we find that thehuman cardiovascular system occupies a middle ground. Averagehuman blood pressure lies between that of ungulates, in whom meta-bolic processes predominate, and that of rodents, in whom the sensory-nervous system is dominant. Another neglected but significant differ-ence between human circulation and that of other vertebrates lies in thedevelopment of arteriovenous anastomoses. Generally speaking, theyappear only in warm-blooded animals and supply the physiological basis


of independent thermoregulation. The development of anastomosesmakes it possible to short circuit large portions of the system of periph-eral capillaries, excluding them from circulation in order to concentratewarmth in the central parts of the body. In birds such anastomoses arefound only in the toes and webbed feet; in mammals, they are onlyfound in the fingers and toes and in parts of the face. Only humans havesuch short circuits distributed throughout the body just under the skin.Although we human beings achieve independent thermoregulation, wedo not maintain either a constant and exceptionally high body tempera-ture, like birds, or an exceptionally low temperature, like whales. Theunique aspect of human thermoregulation consists in its rhythmicalchanges that are clearly correlated with changes in consciousness. Fig-ure 8 illustrates the shift in the concentration of warmth in the humanbody from day to night. At night, when we sleep, our circulation opensto the surrounding space, which is why we need to cover ourselves.

Fig. 8: Diagram of isotherms in the body at environmental temperatures of 20o C and 35o C[adapted from Aschoff].

36oC isotherm37oC isotherm

diurnal nocturnal

20oC 35oCenvironmental temperature


By day, when we are awake and aware of ourselves and go about ourwork, thermoregulation centralizes our circulation, thus creating aspace separate from the external world.

As we see, the human being has become an individual microcosmwith regard to all seven organ systems, evidently a requisite phenome-non for the spirit to be self-reflective and self-determining within thehuman body.

Clearly, increasing differentiation of the heart and arterial vascularsystem accompanies the development of affective and cognitive abili-ties, as we observed in the phylogenetic sequence of animals leadingup to the human being. Among the lower vertebrates, venous circula-tion preponderates and little internalization of psychological activityoccurs. In contrast, in the higher vertebrates, and especially in humanbeings, both arterial circulation and increasingly alert and internalizedpsychological activity have evolved.

Conclusion

Let’s summarize the characteristic steps in the evolution of the car-diovascular system. In insects, we find a highly specialized sensory sys-tem that is not centralized and an open circulatory system in which theblood flows freely throughout the body. In fish, the central nervous sys-tem develops, accompanied by a closed vascular system, but onlyvenous blood flows into the heart. In amphibians, internalized respira-tion is reflected in the functional separation of the arterial and venousblood streams in the heart. At the reptilian level, fluid regulation isinternalized and the two types of blood are morphologically separatedin the heart, although this separation remains incomplete in the vascu-lar system. In the warm-blooded birds all organ systems are suppliedexclusively with arterial blood, a phenomenon that seems to provide aphysiological basis for the development of an alert psyche. The higherdegree evolutionary emancipation from the environment representedby mammals involves completely internalized reproduction. The great-est degree of emancipation is reached in human beings, who, centeredin themselves, can be self-reflective and self-determining, directingtheir own actions on the basis of individual judgment.

In the successive evolution of the seven organ systems as described


here, the involvement of each new system reflects back on the organ-ism as a whole. But the evolution of individual organs is not completewhen they are first released from environmental constraints. Theyundergo further differentiation at each successive level. From this per-spective, it is easy to acknowledge that the sensory-nervous system withthe brain is the most highly evolved of all organ systems and is there-fore able to serve as a foundation for the thinking and self-determin-ing human spirit.

References and Bibliography

1. Aschoff, J. 1971. In Gauter, Kramer, Jung, eds., Physiologie des Menschen.Munich.

2. Benninghoff, A. 1931. Die Architektur des Herzmuskels. Morpholog. Jahr-buch 67.

3. Kipp, F. 1948. Höherentwicklung und Menschwerdung. Stuttgart: Verlag FreiesGeistesleben.

4. Portmann, A. 1969. Einführung in die vergleichende Morphologie der Wirbeltiere .Basel: Schwabe.

5. Schad, W. 1965. Stauphänomene am menschlichen Knochenbau. In Goet-heanistische Naturwissenschaft (Anthropologie) Bd. 4. Edited by W. Schad. Stut-tgart: Verlag Freies Geisesleben, pp. 9-29.

6. Schad, W. 1969. Die Ohr-Organisation. In Goetheanistische Naturwissenschaft(Anthropologie) Bd. 4. Edited by W. Schad. Stuttgart: Verlag Freies Geistesle-ben, pp. 173-189.

7. Schad, W. 1977. Man and Mammals. Garden City, NY: Waldorf Press.

8. Schad, W. 2002. The Dynamic Morphology of the Heart and CirculatorySystem. (See W. Schad’s chapter in this book.)

9. Starck, D. 1982. Vergleichende Anatomie der Wirbeltiere. Berlin/Heidelberg:Springer Verlag.

6

T h e E m b r y o n i c D e v e l o p m e n t o f t h e C a r d i o v a s c u l a r S y s t e m

M A T T H I A S W O E R N L E

P R E F A C E B Y

H E I N R I C H B R E T T S C H N E I D E R

P R E F A C E

(Heinrich Brettschneider)

IN THE SEVENTEEN YEARS that have elapsed since Matthias Woernlewrote the paper reprinted here, the field of embryology has under-gone a veritable revolution. The author himself was unable to revisehis work accordingly, so we must be aware that it contains someviews unsupported by current perspectives. So why reprint it?Woernle’s work is exemplary inasmuch as it seemed fully supportedby the sensory evidence available at that time, and his overall pictureof developmental relations remains stimulating. Perhaps even moreso than its “correct” conclusions, its “errors” are instructive. Theycaution us never to pause in our search for the truth, which is of


course infinite, and to be skeptical whenever the results of the latestresearch are presented as the ultimate answer, for they too will soonbe outdated.

We will begin our “update” of Woernle’s essay with some aspects ofgeneral human embryology which, although not exclusively relatedto the development of the cardiovascular system, are mentioned inWoernle’s paper and need to be corrected in view of more recentfindings. With regard to the early development of embryonic tissues(see pp. 125 ff.), only the chorionic epithelium develops out of thetrophoblast.

With the exception of the chorionic epithelium, all embryonicand extraembryonic tissues develop out of the embryoblast. Theamniotic cavity does not develop between the ectoderm and the tro-phoblast. Rather, it develops as a fissure in the primitive ectoderm(or epiblast). And finally, the initial “mesenchyme” develops out ofthe primitive endoderm or hypoblast rather than from the tropho-blast [10, 18].

Since the early "mesenchyme" develops out of the primitive endo-derm, the earliest origin of blood cells and blood vessels in the humanmust also be revised. According to the works of Fukuda (1973, 1978,quoted in [32]) and Takashina [32], the earliest blood cells and bloodvessels of the human are not formed out of mesoderm, but out of theprimitive yolk sac endoderm of the secondary human yolk sac. Thisprocess is specific to the human being, the great apes and the simians(New and Old World Monkeys), but not Prosimians (such as lemurs)and not other mammals, and does not contradict the classical findingthat blood cells and vessels are of mesodermal origins later on in devel-opment. The details of this unique embryological process in thehuman being and the higher primates must be taken from the cited lit-erature. But here we show a summary by reproducing two of Takash-ina’s figures (see Figures 1 and 2).

The conclusion that humans as well as higher primates (anthro-poid apes and monkeys) differ from most mammals in key respects isa result of a multiple paradigm shift that has occurred in compara-tive embryology since the time when Woernle’s paper was written.This shift is discussed in greater detail in a more recent work by thisauthor [3].

Th e E m bry on i c De v e l opme n t o f t h e Car d i ov as cu la r S y s t e m 1 1 7

Fig. 2: Takashina’s view of blood cell and blood vessel development in the yolk sac wall.

A: A blood island is formed in the endoderm. B: The endoderm around the blood island differ-

entiates into mesenchyme. C: Primitive capillary; the endoderm develops into blood cells and

mesenchyme; the mesenchyme differentiates further into endothelial cells.

Heart Formation

The formation of the heart in the human being, mammals, and ver-tebrates in general, is probably one of the most controversial subjectsin embryology, and can only be discussed in the context of method,that is, in the context of evolving scientific paradigms. The classic para-digm of the development of the human heart, first formulated byHensen (1876), and here reproduced by Woernle, derived its essentialelements from the study of rabbit embryos [14]. Hensen interpretedthe first traces of large blood vessels near the anterior portal of theprimitive gut as a tube-like pair of cardiac primordia and assumed thatthey later united posteriorly into a single tube in the course of thefusion of the lateral walls of the anterior intestinal portal.

Fig.1: Classical description of blood cell and blood vessel formation. A: Undifferentiated mes-

enchyme. B: Formation of angiogenic cell clusters. C: Primitive capillary; the mesenchyme

develops into blood cells and endothelial cells (From [32]).

yolk sac endoderm blood cell

mesenchyme cells blood island endothelial cell

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yolk sac endoderm mesenchyme cells blood cell

blood island endothelial cell

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This view of a tube-like bipartite heart primordium that was fusedby closure of the primitive gut was widely supported by animal studies,e.g. by Patten [24], Hamburger and Hamilton [12], Bellairs [2], DeHaan [6], and also repeatedly described in the human [5, 22]. Butthis view came into question from the 1960s on: De Haan [7] andRosenquist and De Haan [26], studying the chick, postulated that theheart arises from a single, horseshoe-shaped part of mesoderm infront of the embryo rather than from a paired primordium. This sec-ond theory, the theory of a so-called pregut cardiogenic crescent,although shortly after contradicted by the same author [29], seemedsuperior to Hensen’s view, even more so when it was demonstratedthat the two sides of the primitive gut do not fuse at all (Seidl and Ste-ding in [16]). Also in the chick, Pantke showed in the early 1980s thatthe lumen of the heart develops out of a loose grouping of manysmall vesicles that converge in the midline, forming a so-called plexusor network in front of the primitive foregut [23]. This latter perspec-tive seemed reason enough to discard Hensen´s view of a bipartite ori-gin of the heart altogether and to explain the observations of Patten[24] purely as a consequence of erroneously taking the precursors ofthe cardinal veins for heart primordia, which—unlike the primitiveheart—are already hollow and tubelike at this early stage. (See Figure3, which corresponds to Figure 3 in [23]; this illustration is also repro-duced in [1] and [16].)

Fig. 3: Graphic reconstruction of the endocardium-lined lumina in the region of the future

heart (Stage 8, Days 16-18). The posterior cardinal veins (v), which appear relatively closed,

are still not connected to the many vesicles in the center of the primordial heart (according to

Pantke, as quoted in [8]).


But now comes the most astounding discovery: Pantke [23] startedher observations in the chick from Hamburger & Hamilton (HH)stage 7 (when the first pair of somites are formed). Since the 1990snew methods made it possible to investigate much earlier stages and totrace cell commitment more accurately and further back than before[4, 25].Now it seems clear that in the chick the prospective heart occu-pies much of the rostral half of the primitive-streak (excludingHensen’s node) at early- to mid-primitive streak stages (HH stages 2and 3), that is, right at the beginning of gastrulation. At HH Stage 4(late primitive-streak stage), ingression of cardiogenic cells is alreadycomplete. During subsequent stages (HH stages 5 and 6, when head-process and head-fold form, but no somites yet), the primordium ofthe heart consists of two flat compartments of mesodermal cells, theso-called heart-forming regions on either side of the head paraxialmesoderm. These mesodermal primordia migrate to the midline andcomplete their fusion into a single straight heart trough shortly beforeHH Stage 9 (seven pairs of somites). This trough is ventrally and later-ally formed by cardiac muscle, whereas its dorsal wall is formed by theventral wall of the foregut. This implies that from their formation totheir fusion, the cells of the heart-forming regions are associated withrostral endoderm.

During stage 6, that is, already at the onset of their midway migra-tion in two cohesive sheets, cells of the paired mesenchymal heartfields start to become epithelial. At first they do not line a lumen, butthen gradually they develop into groups of vesicles as described byPantke, to form a medial cushion of spongy pro-endocardium in HHstage 7. Shortly afterwards, dorsally located cells of the heart-formingregions undergo myocardiac differentiation, already exhibiting rhyth-mic beating while fusion is still in progress. This was first observed inthe chick, but the hitherto reported differences between birds andmammalian species are probably only due to the description of theheart primordium before or after the fusion of the mesodermal com-partments (see [9] with its beautiful drawings of the horseshoe-shapedprimordium after the fusion).

So now heart development is viewed as a fusion of paired primor-dia once again. But these primordia fuse anteriorly and not posteri-orly, as Hensen believed, and the processes are earlier and much more


integrated than hitherto suspected. Now indeed one must speak of amedial fusion of two lateral primordia, but the differentiation pro-cesses of heart muscle and heart lumen are wonderfully integratedinto the fusion and do not precede it.

What can we learn from all this? We can learn how important one’sperspective is when observing phenomena. Clearly, to acknowledgethat two tubes fuse in heart development necessitates viewing the heartfrom the outside. This aspect reveals a characteristic typical of thenerve and sensory system, namely bilateral symmetry. When, in con-trast, researchers viewed the heart from the inside, they identified theorigin of the heart lumen. This perspective shows the lumen develop-ing out of a diffuse plexus or network-like structure, which is charac-teristic of the metabolic system. But whether we see the heart onlyfrom the inside, as Pantke did, or only from its outside, as Hensen did,or whether we see a wonderfully integrated process of organ differenti-ation, makes all the difference. Fighting one perspective with the argu-ments of the other leads nowhere.

Development of the Blood and Blood Vessels

Characteristically, the cardiovascular system is the first organ systemin the human embryo to become visibly functional. The first blood ves-sels appear as early as the twelfth day of gestation, when the embryoitself is nothing more than a membrane consisting of two cell layersand approximately 500 cells where the amnion meets the yolk sac.

When blood vessels first become visible, therefore, the humanembryo is nothing more than a hollow form or blastocyst that isdefined by the surfaces of surrounding tissues and possesses no sepa-rate interior spaces of its own. Thus it is not surprising that the firstblood vessels appear peripherally in the chorion, which is located out-side even the amnion and yolk sac, rather than centrally in the disc-shaped, double-layered embryo itself. At this early stage, the envelop-ing chorion already consists of two types of tissue—the trophoblast,which is in direct contact with the uterine mucosa, and a type of vascu-lar connective tissue that appears in no animal at such an early stage.This connective tissue, although of endodermic origin, is called themesenchyme or mesoderm (from the Greek mesos, middle) because it


has a three-dimensional, meshwork-like structure reminiscent of thelater mesoderm of the primitive streak embryo.

The very first blood vessels to appear are the primordia of the capil-laries, the threadlike vessels that later form the outer limits of bloodcirculation. Strangely enough, these capillaries initially seem to leadnowhere, having blind ends in both directions [15]. They contain nocorpuscles at this stage. The precursors of red blood cells appear onlyon Day 15 of gestation, three days after the first appearance of bloodvessels, and some distance away, in the so-called blood islands on theventral surface of the yolk sac--that is, in a much more central locationthan the first capillaries [11,21, 22]. According to Demir et al., bloodcells are found in chorion capillaries only from Day 21 (Stage 9)onwards [8]. From the very beginning, the blood islands of the yolksac produce two types of cells. The interior cells, the precursors ofblood cells, become round, while the outer cells flatten and mergeinto little sacks which then interconnect, forming a capillary networkon the surface of the yolk sac. This network ultimately releases bloodcells into the chorionic capillary system, ending the initial separationof the elements of blood circulation. As we have seen, the circulatorysystem first develops in the surrounding tissues, but from Day 17onward, capillaries and blood cells are also found in the embryo itself.At the same time, gastrulation—the inversion of surface tissue into theinterior of the embryo—reaches its peak. This process represents afundamental change in that the embryo develops an internal spaceand begins its transformation into an entity distinct from the sur-rounding tissues.

Sonograms reveal heart contractions from Day 23 onward [27].According to Demir et al., however, until Day 28 there is no convincingevidence of a continuous circulatory system that perfuses the entireplacenta with fetal blood [3]. How do these phenomena fit together?

In the past decade, many classical embryological concepts have hadto be abandoned. For example, the old idea that capillaries branchand grow outward from the center is no longer tenable.

It is now apparent that blood and blood vessels first develop inextraembryonic tissues. Quite possibly, all of the blood’s stem cells(hemangioblasts) originate in the blood islands of the yolk sac andonly later move into the chorion and the body of the embryo. In all


probability, therefore, it is more accurate to say that blood cellsmigrate than that capillaries sprout from the center. Admittedly, it isstill unclear whether hemangioblasts migrate singly or in groups. Weare now certain, however, that all blood vessels originally exist as“islands”--that is, as widely distributed but initially unconnected gapsbetween tissues--before merging into plexuses and ultimately into acomplete system of blood circulation.

This decentralized development explains the contradictions inthe times listed with regard to the development of the capillary sys-tem on the fetal side of the human placenta. Initially, only isolatedislands of vessels are present on the surface of the yolk sac and in thechorionic villi. More than two weeks elapse between the appearanceof these first disjunct primordia around Day 12 and their hemody-namically effective consolidation around Day 28. The embryo’slarger vessels also develop multicentrically and form plexuses ratherthan branching outward from the center (Steding and Seidel, in[16]). Even the aorta develops in this way, although it is unique inthat its walls release not only red blood cells but also macrophages(large immune cells).

Fig. 4: The plexiform phase in the primordium of the heart lumen at Stage 10 (Day 22) accord-

ing to a) Sternberg, b) Orts Llorca, c) Ingalls (from [16]).

According to Ingalls, Sternberg, and Orts Llorca, the heart, like anyother blood vessel, develops out of the consolidation of many lumina(cavities) of tiny fluid foci bounded by flattened mesenchyme cells(see Figure 3) [17, 31,20]. From Day 19 to Day 21 of gestation, thesefissures merge into a plexiform lumen (see Figure 4 a-c). According to

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Steding et al., vesicle consolidation begins in the lower part of the bodyand spreads toward the head—that is, larger lumina appear in the cau-dal portion while the plexiform condition still persists in the cranialportion [30]. Heart contractions, however, begin around Day 21,before the connection is established between the umbilical veins lead-ing to the heart and the arteries leading away from the heart toward thebranchial arches (Seidel and Steding in[16]). Sonographic images ofliving embryos in situ reveal that at this stage the systole is not yet a uni-formly centripetal contraction. Rather, it is a wavelike motion thatresembles intestinal peristalsis and works from below upward [16].

Fig. 5: Diagram of the earliest blood vessels in a human embryo at Stage 9 (Days 19-21,

according to Ingalls, from [16]). The amnion (A) is shown opened; crosshatching indicates the

ectoderm of the embryo. Only isolated islands of vessels (V) are visible on the surface of the

yolk sac and in the chorion. The heart lumen (L) is in the plate plexiform phase, and the aorta

is not yet hollow over its entire length. Even the umbilical vein, the largest vessel at this stage

of development, still dead-ends near the body stalk and is therefore out of reach of the heart’s

influence. And yet the heart is already beating rhythmically!

Ingalls’ depiction of a Stage 9 embryo (Figure 5) clearly character-izes the discontinuous, multilocular primordium of the embryonicsystem of blood circulation [17]. The lumen of the heart enters the

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so-called tubular phase only toward the end of Stage 9 (Day 21). OnDay 22 (Stage 10) the tubular heart begins to bend, and the cardiacloop is completed within 18 to 24 hours (Day 23). Classical views ofthis stage of heart development—namely, that the cardiac loop resultsfrom the constraints of growth [24] or is caused by the blood stream[28] are no longer tenable. The mechanics of growth do not explainwhy the heart loops to the right in 99% of cases, and the blood stream,which appears only after the heart, cannot cause the heart’s shape.

What are the consequences of these findings? The heart has beenbeating for a week before a lumen exists to serve as a conduit for theblood. In other words, cardiac rhythm precedes the flowing of theblood. Embyrologists have discovered that that blood movement andcardiac activity are independent phenomena, and that the heart beginsto beat before its beating makes sense in terms of driving the blood.

These phenomena suggest an extraordinary similarity betweenhuman thinking and the earliest processes in cardiovascular develop-ment: Nature designs the form of the embryo in broad strokes andwithout material continuity, just as a human spirit would do. Archi-tects charged with providing appropriate infrastructure for a develop-ment would proceed in the same way. They would certainly notdetermine the location of roads and intersections by watching for traf-fic patterns to emerge from the chaotic circulation of cars and trucksallowed to drive wherever they choose. Instead, architects apply a pro-cess similar to the formative processes of the human embryonicperiod. The first step is to grasp the total scope of the project and stakeout the periphery, so to speak. (In the human being, this stage ismarked by the development of capillaries in the tissues enveloping theembryo, and especially in the chorion.) Marking the boundaries canbe a sketchy and provisional process at first, because as yet no cars aredriving around. Perhaps a bridge will go here and an intersectionthere, but for the moment everything in between is left blank. Themain point is that the planning board knows where things are head-ing. Once the most important locations have been assigned, the restcan be filled in relatively quickly. The separate portions of the systemare connected in a very short time, and after four weeks (the time ittakes for the first buds of arms and legs to appear in the embryo) thewhole structure comes together.


By demonstrating that the heart’s movement and blood flow are ini-tially independent of each other, developing separately in space andtime, embryology can help us transcend the prevailing narrow viewthat relates cardiac activities only to circulating the blood. Rather, ourminds can once again become open to seeing. And as soon as we beginto take phenomena not just as arguments in service of theory, but asGoethe put it, as things in their own right, the living organism speaksto us on its own behalf.

T H E EM B R Y O N I C DE V E L O P M E N T O F T H E C A R D I O V A S C U L A R S Y S T E M

(Matthias Woernle)

In this paper we will discuss the formative principles at work in theembryonic development of the heart, vessels, and blood. First, however,we must gain an overview of human embryonic development as a whole.

The Early Embryo

As the fertilized human egg (zygote) passes through the Fallopiantube to the uterus, it metamorphoses into a spherical cluster of cells,called a morula (see Figure 6). Beginning with Day 4 of gestation, ablastular cavity, or blastocoel, forms in the cell cluster, which is nowcalled a blasocyst. This cavity is bounded by an outer single layer ofcells called the trophoblast. An area of distinctly different cells pro-trudes into the cavity (see Figure 7). These cells form the embryoblast,the center of actual embryonic development. Most of the embryo’sown organs emerge from the embryoblast. In contrast, the tropho-blast, which develops on the periphery, gives rise to the envelopingmetabolic organs that link mother and infant and are cast off at birth.1

Around Day 6 of gestation, the blastocyst implants itself in the uterine

1. Editor’s note: Only the chorionic epithelium develops out of the trophoblast. Allother embryonic and extraembryonic tissues develop out of the embryoblast.


mucosa. The embryoblast then differentiates into two distinct cell lay-ers--the endoderm, or germ layer closer to the blastocoel, and the ecto-derm or outer layer (see Figure 8).

Fig. 6: Diagram of division from the 2-cell stage to the formation of a cell cluster (Days 2-4 of

gestation).

Fig. 7: The blastocyst on Day 5 of gestation.

trophoblast

embryoblast

yolk sac


Fig. 8: Schematic representation of a human blastocyst approximately 9 days old. 1: amniotic

cavity; 2: yolk sac; 3: ectoderm; 4: extraembryonic mesenchyme; 5: endoderm; 6: uterine

mucosa; 7: trophoblast.

At the same time, a fissure forms between the ectoderm and the tro-phoblast and begins to develop into the amniotic cavity.2 Prior to thisstage, development involved primarily the trophoblast, with littlechange occurring in the embryoblast. For the moment, we will con-tinue to describe the development of the trophoblast. It gives rise to amesenchyme, or as yet undifferentiated germ layer, that surroundsboth the blastocoel (primary yolk sac) and the embryoblast or embry-onic disk with its amniotic cavity.3 This tissue, the extraembryonic mes-enchyme, lies outside the embryo. Around Day 12, fissures appear in

2. Editor’s note: The amniotic cavity does not develop between the ectoderm and thetrophoblast; rather, it develops as a fissure in the primitive ectoderm (epiblast).3. Editor’s note: The initial “mesenchyme” develops out of the primitive endoderm (orhypoblast) rather than out of the trophoblast.

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the extraembryonic mesenchyme. They grow and merge to form thechorionic cavity, which separates the extraembronic mesenchyme intoan outer layer bordering on the trophoblast and an inner layer enclos-ing the yolk sac and the amniotic cavity (see Figure 9).

Fig.9: Schematic representation of a human blastocyst approximately 16 days old. 1: amnionic

cavity; 2: chorionic cavity; 3: yolk sac; 4: ectoderm; 5: extraembryonic mesenchyme with blood

islands; 6: endoderm; 7: uterine mucosa; 8: trophoblast.

Now let’s turn to the development of the embryoblast. Around Day16, it also develops a germ layer between the ectoderm and the endo-derm. Examined under the microscope, this tissue layer is very similarto the extraembryonic mesenchyme, and like the latter, it too gives riseto circulatory primordia. For this reason, it is known as the intraem-bronic mesenchyme (see Figure 10).

The extraembryonic and intraembryonic mesenchymes differ inboth location and time of their appearance. The extraembryonic mes-enchyme, which develops first, forms a sphere enveloping the futureembryo, while the intraembryonic mesenchyme, which appears later,develops in the embryo’s center. Clearly, the organ-forming forces ofthese two tissues are polar opposites.

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Fig.10: Schematic representation of the development of the intraembryonic mesenchyme.

A: human blastocyst around Day 13; B: human blastocyst around Day 16. 1: amniotic cavity;

2: yolk sac; 3: ectoderm; 4: extraembryonic mesenchyme; 5: endoderm; 6: intraembryonic

mesenchyme.

Maturation begins in the outermost layer of the extraembryonicmesenchyme, where fluid-filled fissures and scattered patches ofdenser tissue begin to develop around Day 13 (see Figure 11).4 Thecolorless liquid that flows in the fissures is a product of the metabolic

4. Editor’s note: The very first blood cells and blood vessels are now thought to formout of the primitive yolk sac endoderm of the secondary human yolk sac. Later in devel-opment all blood cells and vessels are of mesodermal origin (see also p. 121).

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processes of trophoblast growth and can be seen as the first stage inblood formation. Thus the development of the blood’s fluid portionprecedes the differentiation of its various formed elements. In the dis-cussions that follow, we will call this fluid “lymph.”

Fig.11: Successive stages in the development of blood and capillaries. A and B show fluid-filled

fissures and increasingly dense areas (blood islands) in the mesenchyme. C and D show the

formation of hollow spaces (primitive capillary passages) within the blood islands and increas-

ing numbers of freely moving primitive blood cells (stem cells). 1: blood islands; 2: capillary

passages; 3: fluid-filled fissures; 4: stem cells; 5: trophoblast.

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Only a short time later, the cells in the patches of denser tissue beginto differentiate into two types, blood-forming cells (stem cells) and thecells that form the vessel walls (see Figure 11). The stem cells free them-selves from the denser tissue and float freely in the fissures (primitivevessel passages) before any contractions of the vessel walls can beobserved. In contrast, the cells of the vessel walls remain connected inlayers one cell deep, forming capillaries that are barely visible under alight microscope. These capillaries are still functionally permeable andallow certain blood elements to pass back and forth through their walls.Although the capillaries are produced by the same germ layer as theblood itself, they are governed by a formative force that shapes formedorgans. In contrast, the blood is produced by a polar opposite forcethat gives rise to unstructured organs that spread out and flow.

Noticeably later, between Days 18 and 20 of gestation, intraembry-onic mesenchyme cells mature in the head pole of the embryo, form-ing the two bilaterally symmetrical vessels that constitute theprimordium of the heart. Here we see the formative polarity betweenthe center and the periphery of the circulatory system. First the meta-bolic processes of the extraembryonic mesenchyme give rise to freelyflowing lymph. Later, at the opposite pole, the heart, which is subjectto strong shaping forces, begins to develop out of the intraembryonicmesenchyme.

As development continues, an increasingly dense network of capil-laries carrying peripherally flowing blood forms in the extraembryonicmesenchyme. A short time later, when this flow of blood begins to bedirected toward the embryo, there is a clear increase in the develop-ment of vessels leading from the periphery toward the embryo, butblood production slows.

Between Days 24 and 28 of gestation, the capillaries growing fromthe periphery toward the center unite with the cardiovascular systemgrowing outward from the center, forming the basis for a system thatpermits circulation of blood. Prior to this stage, differentiations withinthe vascular system are possible only on the basis of direction of bloodflow; that is, we can distinguish the veins leading from the peripherytoward the heart primordium from the arteries leading from the hearttoward the periphery. The flow of arterial blood becomes rhythmicalonly around Day 28, when the continuity of the arteries is established.


Diagram 1 summarizes what we have discussed thus far.

As described in greater detail below, the fact that the poles of thecardiovascular system mature to different extents further illuminatesthe polarity this diagram presents. Beginning with a discussion of theblood, we will show that the polarity reappears within the blood itselfas the contrast between formed elements and fluid plasma. We will fol-low this with a discussion of the capillaries, veins, arteries, and heart.

The Blood

As we have already discussed, blood is initially colorless. Blood stemcells develop only around Day 13 of gestation, after lymph is first pro-duced. Some of the stem cells remain in their embryonic conditionand migrate into the primordia of the liver and spleen and into thebone marrow. Stem cells persist in the embryonic state for a lifetime inportions of the bone marrow, where they produce white blood cells(leukocytes), red blood cells (erythrocytes), and platelets (thromb-ocytes). In childhood the entire skeleton is capable of producingblood cells, but with advancing age this ability is restricted to spongyportions close to the torso, such as the vertebrae and the head of thefemur. After birth, the blood-forming ability of the liver and spleendeclines, with the liver producing only plasma and the spleen only spe-cific white blood cells (lymphocytes and monocytes). At the same time,when the intake of nourishment from outside begins, these two organsdevelop the ability to absorb, digest, and eliminate blood componentsthat have become inactive. The spleen performs this function forblood cells and the liver for blood plasma (gall formation). Clearly, theproduction of blood moves from the spherical periphery to the inte-rior, and secondary blood-breakdown processes develop to comple-ment the original processes that build up the blood.

Dominance of Primordial circulatory Dominance of

structured organs system fluid organs

Heart primordium Arteries Veins Capillaries Blood cells Lymph


Under the microscope, nucleated white blood cells more closelyresemble stem cells than red blood cells do. White blood cells are self-motile; they can pass through vessel walls, carry out many metabolicprocesses, and absorb and digest organic foreign substances andmicroorganisms. They produce proteins and secrete them into thebloodstream. From a biological perspective, they occupy a middleground between the fluid and formed elements of the blood.

In contrast to leukocytes, erythrocytes mature earlier in the courseof embryonic development. They become nonnucleated, highly struc-tured blood cells. They are only passively motile and cannot passthrough vessel walls. Their chief metabolic accomplishment is bind-ing and releasing oxygen. In comparison to white blood cell metabo-lism, the metabolic activity of erythrocytes is highly restricted andspecialized.

Platelets, or thrombocytes, the third type of blood cells, are ame-boid in form and movement. Their progenitors are large, nucleatedcells that reveal a great variety of shapes under the microscope and canpass through vessel walls. To this extent, blood platelets resemble leu-kocytes. At maturity, however, they resemble erythrocytes in that theylack nuclei, lose the ability to actively penetrate vessel walls, andremain in the blood stream. Their function seems to be to maintainthe density of the vessel walls [13].

Thus we see a polarity between the blood’s cellular components onthe one hand and the system of colloidal, flowing plasma on the other.Leukocytes are more closely related to the fluid pole, erythrocytes tothe structured pole. Thrombocytes occupy the middle ground. Dia-gram 2 summarizes what we have said thus far.

Structured pole Blood Fluid pole

Blood cells Blood plasma

Erythrocytes Thrombocytes Leucocytes


The Capillaries

A polarity can also be found in the capillaries, specifically, betweenthe capillaries of the head and those of the liver. Liver capillaries areexceptionally thin-walled and the spaces between the cells of theirwalls are relatively large, allowing substances circulating in the bloodto enter the glandular tissue of the liver. In contrast, the brain has thethickest capillary walls of any part of the body. They have no pores andallow few substances to pass through. Muscle capillaries fall some-where between these two extremes in terms of both the structure andthe function of their walls, which are neither as thick as those of braincapillaries nor as permeable as those of liver capillaries.

Initially, capillaries throughout the body more closely resemblethose of the liver, but they mature to different extents, depending onthe functions of the organs in question. In this respect, the capillarysystem of the brain is the most differentiated and the most morpholog-ically distinct. Its polar opposite is evident in the loose morphologyand life-long embryonic state of the liver capillary system, which mustbe described in terms of its physiology.

The Veins and Arteries

In contrast to the capillary system, which develops on the spheri-cal periphery, early veins are bilaterally symmetrical in relationship tothe median, or sagittal, plane. We find paired veins in the umbilicusand yolk sac as well as in the embryonic body. In the further course ofdevelopment, the veins of the head preserve their bilateral symmetryto a great extent, while significant transformations occur in the chestand even more so in the digestive system, where the veins on theright side are supplied with more blood as a result of newly formed

Dominance of The capillary system Dominance of

morphological physiological processes

structures

Brain capillaries Muscle capillaries Liver capillaries


anastomoses and grow larger than the veins on the left, which stagnatein their growth or even atrophy. Thus the veins of the mature digestivesystem and torso have emerged primarily from vein primordia on theright side of the body.

The early development of arteries, like that of veins, is bilaterallysymmetrical. As with veins, however, this symmetry persists only in thehead and not in the chest or metabolic system. But while the venoussystem emphasizes the right side as the result of anastomoses that formlater, the arterial system develops predominantly on the left side of thebody. Presumably, the transformation of the arteries, unlike that ofveins, does not result from differences in blood supply on the two sidesbut rather from a narrowing process that proceeds from the vesselwalls (see the discussion of the closing of the ductus arteriosus, below).This suggests that the venous system relates more closely to the forma-tive forces linked to the blood flowing in from the periphery, while thearteries are more closely related to the formative forces that drive ves-sel formation from the center outward.

Having acknowledged the asymmetry of a predominantly right-sidedvenous system and a predominantly left-sided arterial system, we mustnow ask about the qualitative differences between the right and leftsides of the body. We must look at the human form as a whole andinvestigate which organ systems reveal the greatest differences betweenright and left. The organs of the human head, such as the eyes and thebrain, develop in bilateral symmetry in relationship to the sagittalplane, and the strictest bilateral symmetry persists in this part of thebody. In the chest, the lungs and heart demonstrate both bilaterallysymmetrical and asymmetrical tendencies. They are bilaterally symmet-rical in that the lungs have right and left lobes and the heart hasroughly similar right and left sides. They are asymmetrical, however, inthat they are not oriented exactly to the sagittal plane (the axis of theheart and the body’s vertical axis form an angle of approximately 45o)and their two halves are not balanced in size. For example, there arethree pulmonary lobes on the right and two on the left.

Asymmetrical development is most prominent in the digestive sys-tem. The liver, a gland closely related to digestion, is located on theright side and is unilateral in its structure. The many metabolic pro-cesses that take place in the liver (production and transformation of


carbohydrates, proteins, and fats) transform nutrients and adapt themto the needs of the body. With regard to blood formation, we havealready shown that before birth, the liver develops functions originallyfound only in the protective organs enveloping the embryo, but afterbirth, these anabolic processes recede, making way for catabolic liverfunctions (gall formation). Nonetheless, the liver must be described asan organ governed primarily by anabolic formative principles. Thus,the liver is related to the forces that are revealed in the veins and in thefluid elements of the blood. That is why both the venous system andthe liver develop in the right half of the body.

The digestive system also includes the spleen, which is also unilat-eral in its structure but lies in the left half of the body. By changing itsmuscle tone, the spleen, a muscular metabolic system with a well-devel-oped arterial vascular system, takes in greater or lesser amounts of arte-rial blood as needed. Compared to the liver, the spleen is less involvedin blood production before birth (liver 80%, spleen 20%) and developscatabolic functions to a greater extent. Although it retains the ability toproduce a few blood components even after birth, the spleen mustnonetheless be described as a metabolic organ governed primarily bycatabolic principles. Thus the spleen is related to the forces that arerevealed in the arteries and the blood’s formed elements. Hence, boththe arterial system and the spleen develop on the left side of the body.

As we have seen, the venous system is dominated by anabolic pro-cesses and the arterial system by catabolic functions.

The Heart

The heart primordium emerges from two bilaterally symmetricalvessels. Around Day 20, these vessels merge into a single cardiac tubethat lies in the sagittal plane. This tube has five distinct segments. Twosegments constitute the lower entry into the heart, one the primitivechamber, and two the upper exit. At this stage of development, bloodflowing from the periphery into the heart meets no resistance as itflows through the segmented tube. Subsequently, the primitive heartprimordium is gripped by transformative, spiral-forming forces. As aresult, the blood stream encounters resistance, and two flows of blooddevelop alongside each other, while the blood between them is at rest.


In these rest zones, the cardiac septa develop, morphologically rein-forcing the pre-existing functional separation and forming the mor-phological basis for the separate circulation of blood to the lungs andto the body. We will soon see that a single formative impulse drives thedevelopment of the lungs and cardiac septa.

The animal evolutionary tree reveals that gill-breathing fish have nocardiac septa, while lung-breathing amphibians such as frogs have twoseparate atria. As animals become less dependent on aquatic habitatsand increasingly adapt to being surrounded by air, both their lungsand their cardiac septa become more highly developed and differenti-ated. In reptiles the cardiac chambers are almost completely separatedand the circulation of blood to the lungs is distinct from that to therest of the body. These separate circulatory systems are most highlydeveloped in birds, mammals and human beings (see the chapter byChristiane Liesche in this volume). Thus the inner differentiation ofheart and lung are clearly intertwined.

Now let’s consider the development of the cardiac septa in detail.By the end of Week 7 of gestation, the right and left ventricles havebeen separated by the development of the septum, and the interatrialseptum develops at approximately the same time, although it closescompletely only at birth. As the interatrial septum develops, a hole(the ostium secundum or interatrial foramen secundum) forms in it,allowing blood to flow from the right to the left atrium. This holeremains open for the remainder of the gestation period. Clearly, theoriginal, uniform conditions of flow typical of peripheral circulationpersist longer in the atria than in the ventricles. Atrial developmentreveals the working of a principle open to forces proceeding from thematernal organism, i.e., from the environment. The opposite organ-forming principle, which is shut off from the environment and devel-ops independent spaces, is at work in the ventricles. The flowing bloodencounters maximum resistance in the compression that results fromthe contraction of the chamber walls. Thus the ventricles are governedby an organ-shaping, centering force that strives for stasis.

In summary, we can divide the prenatal development of the heartinto three phases. The first phase produces the two bilaterally symmet-rical tubes of the heart primordium, which at this stage is as open tothe environment as our senses remain for life (see Figure 12).


Fig.12: Ventral view of successive stages in cardiac development. A: merging of the two original

bilaterally symmetrical cardiac tubes (around Day 20); B: the combined cardiac tube (around

Day 22); D: formation of the cardiac loop (Days 24-26); E: increasing symmetry of the cardiac

loop (around Day 28); F: the heart divided by septa (around Day 50).

In the second phase, the two tubes join and bend like the intestines.This gesture toward the formation of an independent space provides thebasis for an organ’s functional emancipation from environmentalforces. This type of development is most clearly revealed in the humandigestive system. The transformation that occurs in the third phase ofcardiac development, which is typical of the actual heart itself, reflects acompromise between strict bilateral symmetry and a one-sided spiralconfiguration. Thus the heart becomes an organ that is open to theenvironment yet possesses an independent, enclosed space.

We must still discuss the differences between the prenatal and post-natal cardiovascular systems. We have seen that the primordium of theprenatal circulatory system develops first in the trophoblast anddepends for the most part on the maternal organism’s metabolism andcirculation. The early development of intraembryonic organs is simi-larly dependent on the mother’s body—that is, the early embryo isreceptive to forces that work on it from its surroundings. The sphericalform of the extraembryonic capillary system and the bilateral symmetry

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of the intraembryonic cardiovascular system are the geometric and spa-tial expression of this openness to the environment.

In the second stage of development, the primordia of various organsare transformed to different extents. In the circulatory system, this prin-ciple is revealed in the development of connecting, asymmetrical vascu-lar anastomoses. The transition to asymmetry is the typical geometricand spatial expression of this second developmental phase, which seesthe development of both the ductus arteriosus, or Botallo’s duct, whichcircumvents lung circulation, and the ductus venosus, or duct of Aran-tius, which circumvents liver circulation (see Figure 13).

Fig.13: Schematic drawing of the prenatal circulatory system. 1: ductus arteriosus; 2: right

atrium; 3: right ventricle; 4: ductus venosus; 5: placental artery; 6: umbillical vein; 7: placenta;

8: capillary region of the brain; 9: cerebral artery; 10: cerebral vein; 11: left atrium; 12: hole in

the interatrial septum; 13: left ventricle; 14: capillary region of the digestive system ; 15: liver;

16: umbillical arteries.

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A number of small vascular anastomoses also develop in the diges-tive system and in the limbs, protecting these organs from excessiveoxygenation and favoring an environment that retains carbon dioxide.

In this second phase of development, therefore, polar organ sys-tems develop. On the one hand we have the organs of the upper andleft body, which retain their original formative potentials. They do notdevelop any circumventing vessels, and are therefore pervaded by oxy-gen-rich embryonic blood. They tend to converse their form and arecharacterized by predominantly catabolic processes. On the otherhand, we have the organs of the lower and right body, where the prin-ciple of transformation is most strongly active. These organs are sup-plied with blood rich in carbon dioxide as the result of ampledevelopment of anastomoses, a phenomenon associated with the pre-dominance of anabolic and growth processes.

The third phase of development begins only at birth and is character-ized by dramatic leaps in development. While the second phase pre-pared the way for the development of independent, separate spaces,these spaces actually take shape postnatally. When the infant separatesfrom the mother’s body, the enveloping organs that serve anabolism andelimination are discarded and the baby’s own organs assume these func-tions. For example, the infant’s lungs become active, and in a paralleldevelopment, the ductus arteriosus closes. Consequently, the oxygencontent of the arterial system increases and the carbon dioxide contentof the venous system decreases (see Table 1). Postnatally, liver functionsmature equally quickly, stimulated by receiving external nourishment.Parallel to this development, the ductus venosus atrophies.

How these two anastomoses close reveals the formative principlesrelated to anabolic and catabolic processes. The ductus venosus, whichis located near the liver and contains no nerves, begins to be blockedby cell proliferation within minutes of birth and is fully closed within amaximum of two months [19]. In contrast, the muscle-rich ductusarteriosus, which is located close to the lungs, does not becomeblocked but begins to close as the result of a reflex-like contraction ofthe vascular wall. Nevertheless, complete closure occurs only when thiscontraction is supplemented by growth processes, although these aresignificantly weaker in the region of the ductus arteriosus than theyare around the ductus venosus. Consequently, the ductus arteriosus


usually does not close completely until twelve months after birth.These postnatal developments demonstrate that maturation is prima-rily due to growth processes in the lower and right body but is domi-nated by neural, catabolic processes in the upper and left body.

Table 1

A characteristic change in circulation also occurs in the heart at themoment of birth, when a membrane seals the aperture in the intera-trial septum. Thus the process of developing an independent and sepa-rate space, which occurred prenatally in the ventricles of the heart, isextended postnatally to the atria. As a result, circulation to the bodyand lungs is so completely separated that significant mixing of blood inthe center of the circulatory system is no longer possible. This phenom-enon is also associated with sudden increases in blood pressure andresistance to flow in the arterial vascular system. In other words, defini-tive differentiation between the arterial and venous vessels occurs onlyduring this third phase of development. This differentiation isachieved through maturation at the center of the circulatory system, asthe heart and arteries become self-contained, independent spaces.

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In conclusion we can state: The functional task of the entire car-diovascular system is to unite the anabolic processes that predominatein the lower body with the catabolic processes in the upper body. Inthis way the human cardiovascular system serves as the mediating prin-ciple in the human organism.

References

1. Bavastro, P. and C. Kümmel, eds. 1999. Das Herz des Menschen. Stuttgart:Verlag Freies Geistesleben.

2. Bellairs, R. 1953. Studies on the development of the foregut in the chick blasto-derm II. The morphogenetic movements. J. Embryol. Exp. Morphol. 1: 369-397.

3. Brettschneider, H. W. 1999. Die teilweise Integration der Embryonal-hüllen bei den Säugetieren und beim Menschen. Tycho de Brahe Jahrbuchfür Goetheanismus, pp. 207-303.

4. Colas, J.F. et al. 2000. Evidence that translation of smooth muscle alpha -actin mRNA is delayed in the chick promyocardium until fusion of thebilateral heart-forming regions. Dev. Dyn. 218:316 - 330.

5. Davis, C.L. 1927. Development of the human heart from its first appear-ance to the stage found in embryos with twenty paired somites. Contrib.Embryol. 19:245-284.

6. De Haan, R.L. 1959. Cardia bifida and the development of pacemakerfunction in the early chick heart. Dev. Biol. 1:586-602.

7. De Haan, R.L. 1963. Organization of the cardiogenic plate in the chickembryo. Acta Embryol. Morphol. Exp. 6:26-38.

8. Demir, R. et al. 1989. Fetal vasculogenesis and angiogenesis in human pla-cental villi. Acta Anat.136:190-203.

9. De Ruiter et al. 1992. The development of the myocardium and endocardiumin mouse embryos. Fusion of two heart tubes? Anat. Embryol. 185:461-473.

10. Enders, A. C. and B. F. King. 1988. Formation and differentiation ofextraembryonic mesoderm in the rhesus monkey. American Journal of Anat-omy 181:327-340.

11. Evans, H. M. 1911. Die Entwicklung des Blutgefäßsystems. In F. Keibel and F.P. Mall, eds., Handbuch der Entwicklungsgeschichte des Menschen: Band 2. Leipzig.

12. Hamburger, V. and H.L. Hamilton. 1951: A series of normal stages in thedevelopment of the chick embryo. J. Morphol. 88:49-92.

13. Hauck, G. 1971. Organisation und Funktion der terminalen Strombahn.In Physiologie des Kreislaufs: Band 1. Berlin: Springer Verlag.

14. Hensen, V. 1876. Beobachtungen über die Befruchtung und Entwicklung desKaninchen und Meerschweinchens. Z. Anat. Entw. Gesch. 1:213-273 and 353-423.


15. Hertig, A. T. 1935. Angiogenesis in the early human chorion and in theprimary placenta of the macaque monkey. Contrib. Embryol. (CarnegieInstitution, Washington, DC) 25:37-81.

16. Hinrichsen, K. V. (Ed.). 1990. Humanembryologie. Berlin: Springer.

17. Ingalls, N. W. 1920. A human embryo at the beginning of segmentation,with special reference to the vascular system. Contrib. Embryol. (CarnegieInstitution, Washington, DC) 11:61-90.

18. King, B. F. and A. C. Enders. 1993. Comparative development of the mam-malian yolk sac. In F. F. Nogales, ed., The human yolk sac and yolk sac tumors.Berlin: Springer.

19. Moll, W. 1971.Fetal- und Placentarkreislauf. In Physiologie des Kreislaufs:Band 1. Berlin: Springer Verlag.

20. Orts Llorca, F. 1934. Beschreibung eines menschlichen Embryos mit 4Urwirbelpaaren. Z. Anat. Entw. Gesch. 103:765-792.

21. O-Rahilly, R.1973. Developmental stages in human embryos. Part A:embryos of the first three weeks (stages 1 to 9). Carnegie Institution Publica-tion 631 (Washington, DC).

22. O-Rahilly, R. and F. Müller. 1987. Developmental stages in humanembryos. Carnegie Institution Publication 637 (Washington, DC).

23. Pantke, G. 1981. Die Entstehung des Herzlumens. Diss. Göttingen.

24. Patten, B. M. 1922. The formation of the cardiac loop in the chick. Am. J.Anat. 30:373-397.

25. Redkar, A., et al. 2001. Fate map of early avian cardiac progenitor cells.Development 128:2269-2279.

26. Rosenquist, G.C. and R.L. De Haan. 1963: Migration of precardial cells inthe chick embryo: a radiographic study. Contrib. Embryol. 263:113-123.

27. Schaaps, J.-P. 1992. Ultrasound features of the early gestational sac. In E. R.Barnea, J. Hustin, E. Jauniaux, eds. The first twelve weeks of gestation. Berlin.

28. Spitzer, A. 1923. Über den Bauplan des normalen und mißgebildetenHerzens; Versuch einer phylogenetischen Theorie. Virchows Arch. (A)243:81-272.

29. Stalsberg,H., and R.L. De Haan. 1969: The precardial arcus and formationof the tubular heart in the chick embryo. Dev. Biol. 19: 128-159.

30. Steding, G. et al. 1980. Die Entstehung des Endocards. Untersuchungenan Hühnerembryonen. Verh. Anat. Ges. 74:365-367.

31. Sternberg, H. 1927. Beschreibung eines menschlichen Embryos mit vierUrsegmentpaaren, nebst Bemerkungen über die Anlage und frühesteEntwicklung einiger Organe beim Menschen. Z. Anat. Entw. Gesch. 82:142-240.

32. Takashina, T. 1993: Histology of the secondary human yolk sac with specialreference to hematopoiesis. In F.F. Nogales (Ed.): The Human Yolk Sac andYolk Sac Tumors, Berlin: Springer. pp. 48-69.


A P P E N D I X A

H e a r t A n a t o m yIt is impossible to draw the heart from one perspective and illuminate its structure.The ventricles, for example, do not lie neatly side-by-side. Rather, the right ventriclelies in front of the left ventricle, which extends below the right ventricle and forms thetip (apex) of the heart. The four chambers do not lie in one plane.

As a teacher I always struggled with this problem: How can I help the studentsget an overview of the heart’s structure and the arrangement of the different majorvessels without terrible oversimplification? When I had time in a course, I modeledthe heart with the students, which was a wonderful project, giving the students atangible sense for its complexity. But this was often not possible, so I resorted todrawings like the one on this page.

It is a compromise, since it depicts all the chambers in one plane. But it is less sche-matic than many drawings and usually elicits comments such as, “that’s much too com-plicated, how are we ever to learn all those parts and draw such a complex organ?” It’sgood for students to feel a challenge coming, as it were, from the organ itself.

The numbers in the drawing below denote the vessels and heart chambers in theorder of blood flow, beginning before the right side of the heart. The letters labelinternal structures.

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T h e H y d r a u l i c R a m The hydraulic ram is a motorless pump that utilizes the energy of flowing water to pro-vide the pressure needed to raise the water flowing through the pump upward.

Hydraulic ram cycle: (see diagram below)1. The flowing water enters the front chamber via the drive pipe, filling it. When

the pressure builds enough to close the escape (poppet) valve (A), the waterforces open the discharge valve (B).

2. The water then rushes into the air chamber, compressing the air inside, continu-ing until air and water pressure are equal. At this point, the pressure forces thedischarge valve shut and “rams” the water out the exit port (C) and upward inthe delivery pipe.

3. With the discharge valve shut, water again fills the front chamber and the cyclerepeats.

Beginning in the early 1800s, hydraulic rams were widely used in rural areas (i.e.,regions with running streams) as a means of pumping water, especially for single,isolated homes. With a two-meter supply head, the delivery head could be as muchas 60 meters. (See: Center for Alternative Technology tipsheet on the hydraulicram: http://www.cat.org.uk/catpubs/tipsheet.tmpl?sku=07).

Although these pumps are quite simple in design, having few moving parts andno external power source (thus requiring little maintenance), other means ofpumping water became preferable with the arrival of cheap conventional pumpsand cheap power to run them. However, there is now a revival of interest in thehydraulic ram due to the increasing concern about greenhouse gas emissions anddwindling energy supplies.

Websites with information about the hydraulic ram: www.lifewater.ca/ram_pump; www.yin-yang.com/rampumps; www.bae.ncsu.edu (click extension programs, then program areas, then drinking water; then publication search engine, then enter hydraulic ram); www.theramcompany.com.

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A B O U T T H E A U T H O R S

HEINRICH BRETTSCHNEIDER, M.D., currently has a general medical practice in Stut-tgart, Germany. He has been a research fellow at the Carus Institute in Öschel-bronn, Germany since 1975 and has published numerous articles on a Goetheanapproach to physiology. After completing his medical training in Freiburg andHeidelberg, he specialized in internal medicine, working at various hospitals.

CRAIG HOLDREGE is the director of The Nature Institute in rural upstate New York.The Nature Institute is dedicated to research and educational activities applying aGoethean, phenomena-centered method (www.natureinstitute.org). Craig was ahigh school biology teacher in Waldorf schools for 21 years. He teaches at the Wal-dorf High School Teacher Training in Wilton, NH and lectures widely. He is theauthor of the book Genetics and the Manipulation of Life: The Forgotten Factor of Context(Lindisfarne Press, Hudson NY, 1996).

CHRISTIANE LIESCHE studied biology at the University of Tuebingen after graduat-ing from the Waldorf School in Krefeld, Germany. She was a research associate atthe Carus Institute in Oeschelbronn, Germany, from 1981 to 1990. Her researchthemes were the relation of plant metamorphosis to the seasons and also the evo-lution of different organ systems in animals. Since 1991 she has been a high schoolbiology and geography teacher at the Waldorf School in Reutlingen, Germany.

HERMANN LAUBOECK, M.D., practiced as an anesthesiologist for 20 years and nowhas a general medical practice in Dortmund, Germany. In 1979 he began research-ing the physiology of the heart and the circulatory system. He is currently workingon heart support system modeled after the hydraulic ram (www.Lauboeck.de.vu).

WOLFGANG SCHAD, Prof. Dr., has been the director of the Institute for EvolutionaryBiology and Morphology at the University of Witten/Herdecke in Germany for thepast ten years. Prior to that he was a co-director of the Waldorf Teacher TrainingSeminar in Stuttgart, Germany. He was a Waldorf high school science teacher fortwelve years and attended the Rudolf Steiner School in Wuppertal. He is the authorof many influential books and articles concerning the Goethean approach to biol-ogy and science education.

MATHIAS WOERNLE, M.D., practices internal medicine at the Klinik Öschelbronn inGermany and is also a research fellow at the Carus Institute in Öschelbronn, Ger-many. He has published many articles on a Goethean approach to human physiol-ogy and anatomy.

1 4 7

G L O S S A R Y

This glossary by no means includes all the technical terms used in this book. Tech-nical terms that appear only once or twice in a very specific context (in the discus-sions of embryology, for example) are not included; understanding such terms mayrequire careful study of the text, although they are also usually referred to in thefigures. Since the glossary is primarily to help the non-specialist, it includes termsbelonging to the basic vocabulary of the circulatory system. I have drawn liberallyfrom the Oxford Dictionary of Biology (London: Oxford University Press, 2000) andMerriam-Websters Collegiate Dictionary (10th edition, 1999).

Words that are part of the concept descriptions and appear in italics may also befound as glossary entries.

Anastomosis. The union of parts of a branching system so that they intercommuni-cate. In the case of the cardiovascular system it refers to interconnected branchesof blood vessels.

Artery. A blood vessel that carries blood away from the heart. Arteries have muscu-lar, contractile walls and usually carry oxygenated (arterialized) blood. (Exception:the pulmonary arteries carry oxygen-poor blood from the right side of the heart tothe lungs.)

Atrio-ventricular valves. The valves situated between the atria and ventricles thatopen and close during the heartbeat. The mitral (bicuspid) valve has two flaps andis situated between the left atrium and left ventricle. The tricuspid valve has threeflaps and is situated between the right atrium and right ventricle.

Blood plasma. The liquid part of the blood that excludes blood cells.

Bradycardia. A slow heartbeat.

Capillary. The smallest, narrowest type of blood vessel. Capillaries have very thinwalls through which gasses and nutrients can pass between the blood and the tis-sues of the organs.

Cardiac output. The amount of blood flowing through the heart in one minute.

Chorion. A membrane that encloses the developing body in early embryonic develop-ment. Part of the chorion develops into the placenta.

Diastole. The phase of the heartbeat during which the ventricle muscles relax andthe ventricles fill with blood; the opposite of systole.

Endocardium. The inner lining of the muscular wall of the heart (myocardium).

Erythrocytes. The red blood cells that carry oxygen in the blood.

Foramen. An opening in a part or organ of the body.

Heart failure. An insufficiency in heart function that does not allow adequateamounts of blood to reach the organs and tissues. It does not mean that the heartstops beating.

G l o s s a r y


Hematoma. A mass of clotted blood that forms in a tissue, organ or body spaceresulting from a ruptured blood vessel.

Leukocytes. White blood cells; important for various functions of the immune system.

Myocardium. The muscular wall of the heart; the myocardium is thickest in the leftventricle.

Perfusion. The life-sustaining circulation of blood through a given tissue or organ.

Pericardium. A membrane that encloses the heart. A small cavity—the pericardialcavity—exists between heart and pericardium.

Plasma. See blood plasma.

Systole. The phase of the heartbeat during which the ventricles contract and bloodflows out of the heart; the opposite of diastole.

Tachycardia. A racing heartbeat, whether due to exercise or pathology.

Thrombocyte (platelet). Cell fragments in the blood that play an important role inblood clotting.

Vein. A blood vessel that carries blood to the heart. Veins have thin walls and usu-ally carry deoxygenated blood. (Exception: the pulmonary veins carry freshly oxy-genated blood from the lungs to the left side of the heart.)

1 4 9

AAmphibians, 102-105Anastomosis definition of, 147 arteriovenous, 48-49Anatomy, 2Arteriovenous anastomosis, 48-49Aselli, Gaspare (1581-1625), 42-43Arteries blood flow in, 23-27 definition of, 147 development of, 134-136 in the head, 31 morphology of, 28, 31Astrocytes, 37Atrio-ventricular valves definition of, 147Autoregulation, 62-63

BBirds, 107-109Blood (see also blood pressure) and human I, 71 and kidneys, 66-67 arterial, 87 cause of movement, 66-71 clotting, 32 continual change of, 13-14 development of, 120-125, 132-133 oxygen content of, 140-141 plasma, definition of, 147 pressure, 59 in arteries, 23-27 curves, 26 renewal of, 69-70 venous, 83-88 volume, 69 in arteries and veins, 31 Blood-brain barrier, 37-38Blood flow and heart, 71-74 and oxygen, 64-66 and total metabolic activity, 66-73 fetal, 84 in arteries, 23-27 in heart, 10-12 in periphery, 34-35, 62-63

laminar 41 pattern of flow, 72-73 recording devices, 24 velocity, 60-61 velocity curves, 26 venous return, 67Blood pressure, 59 central venous pressure, 63, 68 in arteries, 23-27 curves, 26 Bradycardia, definition of, 147

C Capillaries, 32-37, 66, 79, 134 blood flow in, 33-35 definition of, 147 in liver, 37 lymphatic, 41 prelymphatic, 41 walls of, 35-36Carbon dioxide, 84 Cardiac output, 54, 58, 60 and pacemaker, 57 definition of, 147 factors influencing, 60-63, 70 of artificial heart, 55-56Chorion definition of, 147Circulatory system and human I, 48-51 as a whole, 44-48 at birth, 140-142 Greco-Roman view of, 77-78 high pressure system, 27-32 interplay of center and periphery, 13-15 of fetus 84-85 polarity of center and periphery,

23-51 of amphibians, 88,102-105 of birds, 89-90 107-109 of fish, 88, 100-102 of human being, 48-51, 111-113 of insects, 99-100 of mammals, 109-111 of reptiles, 88, 105-107

I N D E X

I n d e x


of vertebrates, 88-90, 100-111 prenatal circulation, 139Comparative anatomy of heart, 88-90 of vertebrates, 88-90 Crocodile, 88, 90 heart of, 106

DDe Vries, William, 55Diastole, 11-12 definition of, 147

E Embryology (see Embryonic

development)Embryonic development comparative, 84-86 in mammals, 109 of arteries, 134-136 of blood, 116-117, 120-125, 132-133 of blood vessels, 116-117, 120-

125, 134-136 of early human embryo, 125-132 of heart, 80-83, 117-120, 136-142 of veins, 134-136Endocardium definition of, 147Erythrocytes definition of, 147 Excessive pumping syndrome, 63-64Extracellular matrix, 39-41

FFeelings, 2, 15-18Fetal circulation, 84-85Fish, 100-102Fibrinolysis, 32, 37Fontane operation, 73Foramen Definition of, 147Frog, heart of, 104

G Goethe, Johann Wolfgang von

(1749-1832), 4-6Goethean approach to science, 4-6

HHarvey, William (1578-1657), 53, 78Heart,

and blood flow, 13-15, 71-74 and human soul, 2-3, 15-18 and feelings, 15-18, 94 and warmth, 15, 16 artificial, 19-20, 55-57 and cardiac output, 55-56 as a perceptive center, 14-15 as a pump, 6-7, 53-55 inadequacy of model, 55-59, 79 adaptation to needs of organism,

13-15 anatomy, 7-12 blood flow through, 11-12, 72-73 comparative anatomy of, 88-90 development of, 12, 80-83, 117-

120, 136-142 expressions referring to, 15-18 evolution of, 88-90 flow of blood through, 10-12 models of (see models) morphology of, 93-94 muscle fibers, spiral arrangement

of, 7-9 symmetry of, 93-94 transplantation, 95 vortex cordis, 8-9 Heartbeat (see also cardiac output) motions of heart during, 12 during strenuous activity, 13Heart failure definition of, 147Heart Rate variability patterns, 18Hematoma definition of, 148Hemoglobin, 86-87High Pressure System, 27-32Homeothermy, 107Human being individual, 3 physiology of, 1-4 circulatory system, unique

features of, 48-51, 111-113Human I and circulation, 48-51, 7Human thinking, 50Hydraulic ram, 73, 91, 145

IInsects, 99-100

1 5 1

KKidneys and blood, 66-67, 69Kilner, Phillip, 11

LLaminar flow, 41Leukocytes defintion of, 148Liebau principle, 92Liver Capillaries, 37Low Pressure System, 27-32Lung oxygen uptake, 13Lymph, 38-44 discovery of, 42-43 protein content of, 36

MMammals, 109-111Metaphors mechanical, 6-7Microcirculatory System, 38-44Models, mechanical, 6-7, 19 of heart, 90-93 as a pump, 6-7, 53-55 inadequacy of model, 55-59, 79 Morphology, 4-6Myocardium definition of, 148

NNafis, Ibn An (13th Century), 53

OOrganism, dynamic wholeness of, 4-5Oxygen and blood flow, 64-66 consumption by heart, 68 content in blood, 140-141

PPacemaker, 55, 57Perfusion definition of, 148Pericardium definition of, 148Peripheral circulation, 62-63, 79

Physiology human, 1-4 Goethean approach to, 5-6 of heart in relation to soul, 15-18Psychology, 3

RReptiles, 105-107Reproduction in amphibians, 103Respiration in amphibians, 102-103

SSchmidt, Karl (1857-1915), 91Sense organs of insects, 99Soul human, 2-3, 15-18Starling’s law, 54, 64Steiner, Rudolf (1861-1925),

preface page, 91Stress, 17Symmetry in development of blood vessels,

135-136 of organs, 93-94Systole, 11-12 definition of, 148

TTachycardia definition of, 148Thermoregulation in humans, 49-50, 112Thrombocyte definition of, 148

VVeins, 28-32 development of, 134-136 in the skull, 30 morphology of, 29-31Vortex cordis, 8-9

WWarmth and heart, 15, 16 in human body, 49-50, 112Work performed by body and heart,

67-68

I n d e x

The essays in this book are inspired by a Goethean view of the organism

and of science. They are an attempt to “portray rather than explain.” Some

essays give precise descriptions of physiological processes, while others

portray the heart and circulation within broader developmental and

evolutionary contexts. The intricacies of the circulatory system and its

place within the whole human being come into view.

Written by doctors, scientists and teachers, the contributions in this

book present a dynamic picture of the circulatory system that both

balances and puts into perspective the prevailing one-sided mechanical

explanations that dominate science and medical education. High school

and medical students today do not usually learn “the heart has functions

that can be interpreted in terms of a pres sure pump”; rather, they learn

“the heart is a pump,” meaning that’s all it is. When a metaphor is taken

as a fact and becomes the sole lens through which one looks, the rich-

ness of reality recedes behind the sharp and narrow focus. One aim of

this book is to transcend this narrow view and to begin to restore life

to our under standing of the heart and circulation.

This book will fill a long-existing void in the literature. It will stimulate

teach ers, health professionals, scientists and lay people seeking a dynamic

perspective on human physiology that is both detailed and comprehensive.

Published byThe Association of Waldorf Schools of North America 38 Main Street

Chatham, New York 12037

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