1  

B  E  N  J  A  M  I  N        K  E  L  L  E  Y    

                                   The   foramen   magnum   is   a   threshold,   a   three-­‐dimensional   aperture   that   resides   at   the   base   of  the  skull,  a  protected  anatomical  position.    The   foramen   magnum   is   a   hole,   a   passageway  from   the   postcranial   to   the   cranial.   A   gateway  from  the  physical  to  metaphysical  chambers.    A  void.    To  observe   its   geometry,   to   ascertain   its  physical  dimension   is   an   attempt   to   further   define   the  human  form,  mechanically,  anatomically.    

           

 

  2  

   Foramen  Magnum  (for  the  measure  of)  Pelican  1200  case,  rubber,  gigli  saw,  inside  calipers,  scalpel,  clipboard  4.87”  x  10.62”  x  9.68”  (closed)  2013  –  edition  of  three          A   collection   of   instruments   selected   for   the  specific   task   of   measuring   the   Foramen  Magnum.    fo-­‐ra-­‐men  mag-­‐num:  noun    Definition:  the   opening   in   the   skull   through   which   the  spinal   cord   passes   to   become   the   medulla  oblongata.    Origin:    New  Latin,  literally  Large  opening    

First  known  use:  1857    (Merriam  Webster  Dictionary)    The   instruments   are   housed   within   a  waterproof,   crush   proof,   pressure   regulated  case,  the  Pelican  1200.    Instruments:    Gigli   Saw   –   a   wire   bone   saw,   compact   and  versatile.  Inside  Calipers  –  to  gauge  dimensions.  Scalpel  -­‐  #3  scalpel  with  removable  #11  blade.  Clipboard  –  Data  recording  

  3  

   

  4  

Method  of  Measurement:    “Maximum   length   of   the   foramen   magnum  (LFM)   measured   in   an   anteroposterior  direction   along   the   principal   axis   of   the  foramen.    Maximum   width   of   the   foramen   magnum  (WFM)   measured   approximately  perpendicular  to  the  LFM  and  recorded  at  the  widest  transverse  diameter  of  the  foramen.      Circumference  of  the  foramen  Magnum  (FMC)  measured   by   pressing   a   narrow   strip   of  calibrated  paper  along  the  inner  margin  of  the  foramen   magnum.   The   paper   strip   is   then  unrolled  and  measured  with  calipers.    Formulae:    The  LFM,  WFM  and  FMC  can  be   inserted   into  on  the   three   formulae  to  estimate   the  area  of  the  foramen  magnum.    The   first   method   is   a   formula   pub;ished   by  Routal  et  al.  ,  which  is  based  on  the  height  (h)  and  width  (W)  of  the  foramen  magnum.    Area  =  ¼  x  PI  x  W  x  h    The   second   method   is   a   formula   derived   by  Teixeira,  which   also   uses  width   height   of   the  foramen  magnum.    Area  =  PI  x  ((h=W)/4)2    

The   third   method   is   a   formula   published   by  Gapert,   Black,   and   Last   and   uses   the  circumference  (C)  to  estimate  the  radius  (r)  of  the   foramen   magnum,   assuming   it   to   be  circular.   This   radius   is   then   applies   to   the  formula  for  the  area  of  the  circle.    C  =  2  x  PI    x  r     Area  =  PI  x  r2”    (Black,  Gapert,  Last.    P1-­‐9).    

 Ventral   view   of   human   skull.   Photograph   by  Benjamin  Kelley.      

Cranial  base  demonstrating  the  foramen  magnum  measurements:  dashed  line  FMC,  vertical  arrow  LFM  and  horizontal  arrow  WFM  (Black,  Gapert,  Last.    P1-­‐9).

           

         

  5  

Works  Cited:    Black,   Sue.   Gapert,   Rene.   Last,   Jason.   “Sex   determination   from   the   foramen  magnum:   discriminant  

function  analysis  in  an  eighteenth  and  nineteenth  century  British  sample.  “  Int  J  Legal  Med.  :  n.  pag.  Web.    

 “Foramen  Magnum.”  Def.  1.  Merriam  Webster  Online,  Merriam  Webster,  n.d.  Web.  12  Nov.  2013.      Works  Consulted:    Matthews,  Washington.  “On  Measuring  the  Cubic  Capacity  of  Skulls.”  National  Academy  of  Sciences.  

Thirteenth  Memoir.  Volume  III.  Part  2.  Washington  Government  Printing  Office  (1886):  107-­‐114.  Print.  

 Howells,  W.W.  “Cranial  Variation  in  Man:  A  Study  By  Multivariate  Analysis  of  Patterns  of  Difference  

Among   Recent   Human   Populations.”   Papers   of   the   Peabody   Museum   of   Archeology   and  Ethnology,  Harvard  University,  V.  67.  Cambridge  :  Harvard  University  Press,  1978.  Print.  

   Consultants:    Eric  W.  Boyle  ,  Ph.D.     Archivist     National  Museum  of  Health  and  Medicine     Silver  Spring,  MD    Laura  E.  Cutter     Archivist  (Contractor,  American  Registry  of  Pathology)     National  Museum  of  Health  and  Medicine     Silver  Spring,  MD      David  R.  Hunt,  Ph.D.,  D-­‐ABFA  

Physical/Forensic  Anthropologist  Smithsonian  Institution  National  Museum  of  Natural  History  

  Washington  D.C.    Brian  F.  Spatola     Collections  Manager,  Anatomical  Division     National  Museum  of  Health  and  Medicine     Silver  Spring,  MD