THE  CHIMPANZEE  AND  ORANG  UTAN. 
365 
at  the  lower  part,  for  the  insertion  of  muscles  "  in  the  ulna  of  his  specimen  of  Simia 
Satyrus.  This  process  is  less  marked  in  younger  specimens,  but  is  very  obvious  in  the 
skeleton  of  the  Pongo.  It  serves  for  a  more  advantageous  attachment  to  the  pronator 
quadratus,  which  muscle  has  greater  breadth  than  in  Man.  The  length  of  the  radius  to 
the  ulna  is  in  Man  as  1 1  to  12  ;  in  the  Orang  it  is  as  36  to  37. 
The  bones  of  the  hand,  like  those  of  the  fore  arm  and  the  humerus,  recede  from  the 
human  type  in  their  elongated  form  ;  the  bones  of  the  thumb,  however,  are  very  slen- 
der and  short,  and  do  not  reach  to  the  end  of  the  metacarpal  bone  of  the  fore  finger. 
The  bones  of  the  carpus  have  their  ossification  completed  later  than  in  the  human  sub- 
ject, and  allow  of  a  freer  motion  upon  each  other.  The  os  pisiforme  is  divided  into 
two,  so  that  the  number  of  carpal  bones  is  nine.  The  proximal  phalanges  of  the  fingers 
are  more  curved  than  in  Man,  and  the  lateral  ridges  more  strongly  developed  than  in 
the  Chimpanzee.  The  distal  phalanges  are  more  pointed,  not  expanding  at  their  extre- 
mities to  give  support  to  an  extended  surface  of  dehcate  touch. 
As  the  upper  extremities  exceed  in  length  those  of  the  Chimpanzee,  so  the  lower  ex- 
tremities differ  as  much  in  the  contrary  respect,  preserving  throughout  the  existence  of 
Simia  Satyrus  much  less  than  the  fully  grown  foetal  proportions  of  the  human  subject. 
The  femur  has  a  straight  shaft,  but  differs  from  the  human  chiefly  in  having  no  de- 
pression on  the  head  for  a  ligamentum  teres^.  The  neck  is  shorter  and  forms  a  more  ob- 
tuse angle  with  the  shaft  of  the  bone,  and  there  is  not  any  linea  aspera  at  the  posterior 
'  In  three  recent  specimens  of  Simia  Satyrus  I  have  found  the  ligamentum  teres  deficient  in  both  the  hip- 
joints.  This  singular  circumstance  in  the  organization  of  the  Orang  Utan  is  not  noticed  in  the  Manuals  of 
Comparative  Anatomy  of  Blumenbach  or  Cuvier,  although  it  has  been  recorded  by  Camper  in  his  Treatise 
on  the  Orang.  (See  OEuvres,  tom.  i.  p.  132.)  It  appears  also  to  have  been  overlooked  in  the  dissection  of 
the  Orang  detailed  by  Dr.  Jeffries  (Boston  Journal  of  Philosophy,  vol.  ii.  p.  570 ;  Philosophical  Magazine, 
vol.  Ixvii.  p.  186.),  unless,  from  the  inference  which  he  draws,  the  hip-joint  of  his  specimen  really  presented 
this  remarkable  exception  to  the  general  structure.  He  says :  "  The  articulation  of  the  femur  with  the  acetabulum 
is  almost  exactly  like  Man's ;  the  neck  of  the  bone  forms  about  the  same  angle.  In  quadrupeds  this  forms  a 
distinguishing  characteristic,  being  in  them  nearly  a  right  angle  :  the  inspection  of  this  joint  is  alone  sufficient 
to  satisfy  the  naturalist  of  at  least  the  facility,  if  not  the  natural  disposition,  of  the  Satyrus  to  walk  erect "  ! 
The  skeleton  is  doubtless  still  preserved,  and  it  would  be  worth  while  to  make  a  re-examination  of  the  head  of 
th.e  femur  to  ascertain  the  presence  or  otherwise  of  the  depression  for  the  ligamentum  teres. 
In  all  the  other  Quadrumana  which  I  have  examined  the  ligamentum  teres  is  present,  but  in  none  of  them  are 
the  legs  so  disproportionately  short  as  in  the  Orang  ;  the  deficiency  of  the  ligament  doubtless,  therefore,  bears  a 
relation  to  this  circumstance,  and  a  greater  flexibility  of  the  hip-joint,  especially  of  rotation  inward,  is  the  result. 
In  the  Unau  {Bradypus  didactylus,  Linn.)  and  Ai  (Brad,  tridactylus.  Linn.),  with  hinder  limbs  of  similar  pro- 
portions to  those  of  the  Orang,  and  habits  still  more  strictly  arboreal,  a  similar  extent  of  motion  is  allowed  to 
the  leg  by  the  absence  of  a  restraining  ligament  in  the  hip-joint. 
In  the  Elephant  and  Megatherium  the  deficiency  of  the  ligamentum  teres  would  seem  to  relate  to  the  position 
of  the  acetabulum  with  reference  to  the  head  of  the  femur,  the  socket  resting  upon  the  ball,  and  not  receiving 
it  obliquely  sideways,  as  in  most  other  quadrupeds. 
In  the  Manis  didactyla,  in  the  Seal,  and  in  the  Walrus,  the  ligamentum  teres  is  wanting.  Rudolplii  and 
VOL.  I.  3  c 
