the outline anatomy of the skull and teeth of mammals of

3

1761

08642641

8

THEOUTLINE ANATOMY

0 E T H E

POLL AND TEETH OEMAMKALS0 P

CANADA

m

INTRODUCTION

IN presenting this compendum on the osteo-

logy of the skulls and teeth of mammals o f

Canada, (exclusive of marine forms),

I haveendeavoured to show,by means of photographs

and drawings, with appended nomenclatures, the

subject matter as clearly as possible, so that

the student of comparative anatomy may be able

to readily comprehend the general formation of

the different animals existing in this country.

The photographs and drawings have been se-

lected from the text of my treatise on " I heOutline Anatomy of the Skull and Teeth of Jfiamm-

als of Canada 1 which have been carefully sel-

ected and re-produced from my osteological coll-ection of North American mammal s , under my own

personal supervision, so that the subject maybemore readily understood.

The subject has been introduced by a c o m-

parative resume^ of some of the lower forms of

Craniata,in order to aid in the study of th e

mammilian forms.

T.C.TRIGGERjD.D. S;L.D. S.

St. Thomas,

Ontario,Canada

DIAGRAM SHOWING THE ARRANGEMENT OP THEENDOSKELETON OF THE HEAD.

Showing the Facial and Cranialgrouping of the bones.

(Total §6- bones.

)

f Pre-maxillaryNasal

Maxillary

Maxfe*vturbinal

Lachrymal --

Mai a r or-Jugal

Manda o 1 e

Hyoid (s).

Frontallyhmoid

TemporalPari etal

Sphenoid

Interparietal

ATALAS

Page 1

THE SKULL,

t f

A Comparative resume.

I

It will be beyond the scope of this compendiumto deal with the primary origin of the skull of theCraniata, but will describe more particularly thebones of the skull and the teeth according to theirdifferent relation to each other, and also give asummary of the comparative osteologioal plan ofstructure which exhist in the lower Vertebratesnamely, Fishes, Amphibians, Reptiles and Birds, toshow their anatomical analogy, in order to" aid in thestudy of the mammalian forms.

In the great vertebral kindom, the fish tribe i

is taken as the starting-point for the study of allother skulls.

It will be observed that the skull of the fishconsists of a great extent of cartilaginous substance,with a considerable less modified fibrous tissue,which may be either more or less fused to thevertebral column or united to it by articulation,none of them having really true bones but mostly ofcalsified tissue. The occipital condyles may besingle, double or entirely wanting.

In some instances there is ho mandable, and inothers only supported by cartilage to the articularelement.

In some instances the jaws are provided withteeth, arranged in rows, in others the teeth havesharp edged plates.

The vomer is usually double and are providedwith teeth, as well as the parasphenoid , thepremaxilla and the maxilla.

Comparatively, the skull of Amphibians whichhave tails, are composed of less cartilage thanthat of bony fishes, also with less number of bones.

There are two condyles always developed, onthe peripheral e xtremity of the skull, on thecaudal aspect, as in mammals.

Page 2

On the dorsal surface of the skull the cranialcavity is enclosed by the frontals and theparietals, and venterally by the parasphenoid

,which

sometimes supports teeth*

The skull of the tailless amphibians (anura)are apparently similar to the tailed ones (Urodeles)

,

but have a more complicated arrangement. On thedorsal side of the skull the tailless varieties arecomposed almost wholly of a cartilaginous boxformation, and in the adult specimens are nptcomposed of so many bones as the Urodeles.

There is a bone which covers the base of theskull- the parasphenoid-which is a prominentanatomical feature.

Prernaxillae are always developed. TheMaxillary bones unite with an intermediate bone-the quadratojugal -which joins the quadrate.

The vomers, two in number, and are character-istic of the skull of all Amphibians. In theethmoidal region there is a characteristic bone,known as the girdle-bone or sphen-e thrnoid. Thelateral walls of the skull remain cartilaginous.

Below the lower side of the palato-quadrate-the pterygoid behind and the palatine in front, thelast mentioned bone is p&aced transversely behindthe vomer.

The Suspensorium has only one bone, -thequadrate-, which is therefore more simple than thatof the fishes.

Among Amphibians they usually have teeth inthe prernaxillae , maxillae, vomers, and dentarypieces of the mandable.

We are now arrived at a very important stagein the osteolcgical structure of Vertebrates,namely Reptiles, in which much of the corilaginoustissue, which compose the skull, has become almostabli terated by extensive process of ossification,thus giving the skull a very solid appearance. Itwill also be readily observed, that the generalstructure of the skull, of the existing Reptiles,

Page 3

when compared with those of Amphibians, is vastlydifferent.

There is a more complete enclosure of thecranial capsule , on the dorsal as well as theventral aspect, and the bones composing them arewell developed.

There is only one occipatal condyle, the sameas birds, in contradistinction to the Amphibia.The parasphenoid, which is such an important bone,on the ventral aspect of the skull, forming theinvesting bone of the roof of the mouth in Fishesand Amphibians begin to disappear, and is replacedby the basioccipital and basisphenoid. In someReptiles, such as the Chelonia the partal bones,are two in number, while in others, they are, asit were, one bone. In all the vertebra of thisclass, the pterygopalatine arch is well developed,and in some of the groups, this bone is movableand free from the base of the skull, while in othersit joins with the corresponding opposite bone inthe median line.

The prootic bone is free in all Reptiles. Theepootic is closely united with the supraoccipatal.

Usually the alisphhenoids and the orbito-sphenoids are wanting, and are replaced by extensionsfrom the parietals, or frontoparietals . The Quad-rate bone in every instance is strongly developed,and in some, Chelonia and crocodile, this bone andthe maxillo-palatine are unmovable to the wall ofthe skull, while in snakes and lizards they are moreor less freely movable. In the Ophidia, forinstance, there is a bone developed between themaxilla and the ptergoid-the ostransversum- . Thesebones have an anatomical characteristic, in as muchthat they are freely movable upon one another andthe cranium, a provision of nature whereby, the oralcavity is capable of considerable distention toallow the seizure of their victim; it also indicatesthat no provision was made for the power ofmastication, but that the remaining part of thedigestive tract is capable of considerable power ofabsorption and assimilation.

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Page • 4

.

The mandable of Reptiles, as well as otherlower Vertebrates is united at the symphisis by astrong elastic tissue, which allow the parts to bedistended laterally according to the needs of theanimal

.

All Reptiles have teeth, except Chelonians,which possess horny sheaths.

The skull of Birds presents peculiarities ofconsiderable interest in the comparative anatomyof Vetrebrates, It will be readily observed thatthey are constructed on a similar outline plan tothat of Reptiles, more strikingly to the order ofLizards. The brain case has increased in size andthe bones of the skull are firm and light, in orderto lessen the weight for rapid flight. There isonly one well defined articular condyle , which isonly necessary, as the long cervical neck changesthe lateral position of the head.

The occipital condyle has become relativelychanged, it lies more up>on the base of the skull,so that it rests at an angle with that of thevertebral column.

In most every instance the bones of the skullare firmly fused together, so that the sutures havedisappeared.

The basi occipital and the basisphenoid formsthe bones of the basis cranii. The roof of theskull is formed mostly by the large frohtals, andthe dorsal edge of the large orbit is formed fromthe frontal. The interorbital septum is welldefined. The ethmoid bone frequently lies upon thesurface of the skull between the nasal and frontalbones. The lachrymal bone is large.

The vomers vary very much in their development.The posterior naries is situated between the vomersand palatine. The squomosal lies closely to theskull, and firmly united to the other bones. Thequadrate bone moves upon the skull, and also formsthe articular joint to the mandable ; the long th

vinquadrato- jugal also unites with it, this latter boneis so situated that it prevents any extreme lateralmovement of the mandable.

.

I

.

l

-

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Page 5

The maxillary bones are small and slender* Thepremaxillary bones unite to form the beak* Thereare large external nasa,l aperatures. The develop-ment of the mandable is essentially the same asthose of Reptiles* The pterygoid bone supports theinner lateral aspect of the quadrate and is directedinwards and forwards to meet the palatine bone, inevery instance the last mentioned bone articulateswith the pterygoid.

Coming now to the highest state of animalexistance namely the Mammalian class of Vertebrates,we find that they have the highest developedorganism, this is particularly noticed in the fullydeveloped skull, in its relative size and form, aswell as the close relation between the cranial andviseral parts of the skull that any previousdescribed vetrebrates. The most prominent featurein the Mammalian series is, the nervous system, ofthe large size of the brain, which has brought abouta large development of the brain capsule, moreespecially that part which received the cerbralhemispheres

.

It will be noticed also, in the fully developedskull, that the maxillary and palatoptergoidsegiinents are united to the skull* As we ascentinto the Mammalian series it is desernable that thebones forming the face lie more below the cranialregion, so that, in Man, this development has beencarried out to a considerable extent, as the facialskeleton is proportionately small when comparedwith the immense development of the cranial partof the skull.

Thus by the Camper method, the intelligence ofthe animal can be ascertained by the progressiveexpansion of the cranium, which can be more or lessaccurately proven, diagramatically , by a line drawnfrom the occipital condyle running along the floorof the nostrils, and also another one touching themost prominent part of the forehead and the labialaspect of the incisor teeth, the angle which theirintersection produce is known as the ’’angle ofintelligence

.

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T.C. TRIGGER, D.D.S

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THE C R A N I A T A.

Q E

( PiscessHeptilia

f Aves*)

7

SKULL OF A DOGFISH (mustelus canis).

(Modified after Parker.)

C. cranium; I. Suspensory ligiment3 of the

jaw8f.nd the cranium and jaws; ha. hyoid arch(

(ventral); hynu hyomftndihular; pq» palito-quadrate; r.c. rostral cartilage; o.c olifactory

capsule; o.f optic foramen; or. orhitjoc. occip-ital; a.c. auditory capsule; f«f. facial foramenm.Mandahle; t. teeth.

THE SKULL 01? A TERRAPIN (TURTLE )

.

E. frontal; pt. prefrontal; f? po 3t-frental;p.pari stal

;so. supraoocipital; coco. occipital-

condyle; ex. exoccipital; "bp. basishpenoid; sq;squmosal; qu. quadrate; quj . quadratojugaljty;tympanum; J. jugal

; Si. interorbital septum;

m.maxilla; pmx. premaxilla;na; nasal ;vo.vomer;

md. mandable; b.s bony seath of the jaw.

LATERAL VIEW OF THE SKULL OFA EOWEL.

AS- angular; ala allsphenoid; ar. articular; apf.anterior palatine foramen; bt. basitemporal; bo.basiocclpital; pbg. basiptergoid; bs. basisphenoid;d. dentary; en. external nostrils; th. ethmoid

;

eo. exoccipital; fr. frontal; f.m. foramen magnum;j. jugal

;1®. lachrymal; mx.p. maxi 11 o palatine

process; mx. maxilla;n. nasal

;px premaxillary;

p*. parietal; ps. presphenoid; pt. ptergoid;

quadrate; q.j. quadratojugal; sq; squmosal; so sup-raocoipltal; ty. tympanium; . romer; of. optic for’m.

THE HYOID BONE OF A BOWEL.

A.body; B. lingual process; E. cornu of lingualprocess and attachment of cartilage; C. 3raall cornuD. large cornu

;E. ligament; G. cartilage exten-

sion of the great cornu, which extends beneath thebase of the skull and extends upward against theposterior part of the cranium, on either side of theoccupit. Compare this bone with the higher mami 1 i anforms.

I

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0 R D E R

G L I R E S. (Gnawers or Rodents.)

EASILY

. Leporidae. (The Hares.)

. Erethizontidae. (The Porcupines.)

. Dipodidae* ( The Jumping Mice.)

4. Geosqyidae. ( The Pouched Gophers.)

5. Mhridae. ( The Mice.)

6. Castoridae. ( The Beavers.)

7. Sciuridae. ( The Squirrels.)

.

> i

DENTAL FORMULA.

( Hares & Rabbits.)

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DENTAL FORMULA,

Squirrel Family (many)

.

A. CROSS-SECTION OE THE SKULL 01 A WOODCOCK.With tile nasal and pre-maxi11ary 'bones removed

to show the olfactory chamber, and position ofthe ethmoid.

B. One-half of the mandable of a Gopherwith the bone sculptered away to showthe relative position of the roots

of the teeth.

>

DENTAL EOKMULA,

THE BEAVER

j 0 - 0 0 0 4-“——4c. — p.m. a.

X 0-—- 0 o—-0 4—— 4

UPPER ASH LOWER TEETH OP A BEAVER

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DENTAL FORMULA

( Rata & the like.)

Deciduous teeth wanting.

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0 H D E R.

INSHCTIVORA- ( The Insect-eaters.)

FAMILY

1. Soricidae. (The Shrews.)

2 , Talpidae. ( The Moles.)

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CHIROPETRA. ( The Bats.)

FAMILY

I. Vesperitillonidae. ( The Common Bata.)

I.

I.

DENTAL FORMULA

C. .L~: T p.m 3-—3 m.3 -3 m 35

2 2 I 1 3 3 3 3"

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I. JNuULATA [ The Hoofed Mammals.)Division A. Perisodactyli ( odd-toed.) j- Horse

DIVISION E. Artiodactyli ( even-toed.

)

=- Hog(a) . Ruminants * Ox(b) . Non-runiments - ^og

FAMILY1. Cervidae (The Deers.)

2. Antilocapridae (The Prong-horns.)

3. Bovidae, ( The Cattle.)

DENTAL FORMULAE

( Horse, Rhinooeros, Tapir and allies.)

HORSE.

c. i_ pS&A»-i3 13 3

After Septimus SissonSb . ,

V. S *

40 or 42

--TEMPORARY--

c £N\ A/ TU M

OCCLUSAL SURFACES OF MOLAR TEEHOF HORSE .

A. Upper Molar* B. Lower Molar.

—TEIGHT-HALF™OF THE UPPER MOLAR TEETH OF

'"AT HORSE. (OCCLUSAL SURFACE* )

All toe valleys and sulsi of both upper and

lower sets are "bounded by enamel, such as the

enanel cot3ring the crown*—— ^

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r A M I L Y

(CERVIDAE.

)

I. Virginia or( Red deer*).

. Wapiti ( Stag.)

. Moose (True Elk.)

. Mountain Aofcelope Prong-horn.)

DEBT AT. FORMULA.

( )x,Buffalo, Sheep, Deer, Antelope, Etc.)

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CATTLE FAMILY .

( Bovidae.)

Hornes hollow inside, never shed, except the prong-

horn; grows hy rings added each year.

1. The Ox ( ho s taurus.)2 . The Sheep ( Ovis aries.)3. Mountain Goat ( Haploceros asountanus.)4. Mountain Sheep ( Ovis Montana.)5. The Musk Ox (Ovihus Moschatus*).

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DENTAL FORMULA,

( PIG & Hippopotaaais.

)

3 I I 4 4

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ORDERFERAE. ( The Carnivora or Flesh Eaters.)

FAMILY

1. Procyonidae. ( The Racoons.)

2. Ursidae. ( The Bears.)

3. Mustelidae. ( The Weasels.)

4. Canidae. ( The Dogs.)

5. Felidae. ( The Cats.)

DENTAL FORMULA.

( BEARS ,RACOONS. ).

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A < •» <r c £ c_ c( v ^ o -j c * # croon,

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DENTAL FORMULA .

( Weasels, Skunks, Badgers, Otters,Wolverines etc.)

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AH APPROXIMATE DRAWING SHOWING THE' MECHANICALCONSTRUCTION OE A COMPLETE GINGLYMUS SO THAT THEMANDIBULAR CONDYLES CARROT BE DISPLACED EXCEPT-ING BY EXTREME ABNORMAL MOVEMENT.

THE GLENOID EOSSAE OR THE WOLVERINE ARE HIGHLYSPECIALIZED IN THIS WAY OWING TO ITS GLUTENOUSNATURE.

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DENTAL FORMULA,

(Dogs, Poxes, Coyote, -wolves .)

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42 .

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ing from the occipital crest to the end of the pre-maxillary suture, add a line drawn fcom the occipitalcondyle passing alone the floor of the nostrils .andanother drawn frrm the most prominent part of thefrontal and the most anterior part of the uoper jaw.

The intersection of these lines wf , .;e Vwill determine the angle of intellegence •

The breadth is determined by a line drawn betw-een the summits of the zigomatic processes*

The Cephalic formula is:

cephalic index.Length

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THE CANTILEVER OH "SUSPENSORIUM " of the FERAEshpwing an approximate drawings of the mechanicalarrangement of the hones supporting the mandahle.

A.VCLFE , B. WOLVERINE

QotMDYLEKPIVOT

" Suspensorium" considerably varies in the

SSw6??

0rder?' cf mammals .that of the HominidaeFamily lies nearly on an horizontal plane.

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DMTAL FORMULA,

(Cat8,Lynx3 and Pumaa.

3 2

B.rAe. ~7~i/rrc </(//>! —

Posterior view of the skull if a catshowing the occipital hones removed, (a.},

and the thin lamana of hone extending fromthe parietals in the form of a 'isurtain*

(h.) dividing the hrain into 2' parts,and alsoto give strength to the cranial

dome*

ORDERPRIMATES ( Anthropod Mammals.)

FAMILY.HOMINIDAE ( The Men.)

SpeciesI Homo ( Man.)

SPECIES, American Indian, and ESQUIMAU

<

DENTAL FORMULA.

Permanent t2—*~2

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TemporaryI. 2 ~2_ C.i

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Sectional view of the mandable, showing the

development of the bicuspid and the

absorption of the roots of the temporary molatbeing 'shed*.

Note at the end of the bicuspid, the soft un-

developed part*

I

THE AHATOiSY OE THE SUPERIOR A1TD LOWER JAWSTHE BONES SCULPURED AWAY TO SHOW THE TEETH

AND TEE NERVE AND BLOOD SUPPLY."Illustration the authors' EducationalLectures on Dental and Oral Hygiene ',whsre

credit is given.

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