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MR.  R.  OWEN  ON  THE  OSTEOLOGY  OF 
part ;  the  inner  condyle  also  is  not  produced  beyond  the  external,  and  the  axis  of  the 
femur  is  consequently  the  same  with  that  of  the  tibia, — a  circumstance  which  may  also 
be  observed  in  Simia  Troglodytes.  In  both  species  the  natural  position  of  the  femur  is 
evidently  a  state  of  inflection  upon  the  pelvis  ;  the  head  must  be  partially  displaced  from 
the  acetabulum  in  order  to  draw  back  the  femur  to  a  line  parallel  with  that  of  the  spine, 
as  may  be  seen  by  comparing  the  figure  of  the  Chimpanzee  (Plate  XLVIII.)  with  that  of 
the  Orang  (Plate  XLIX.).  The  angle  which  the  femur  forms  with  the  trunk  is  more 
obtuse  in  the  Chimpanzee  than  in  the  Orang,  in  which  the  arms  are  better  organized  as 
vicarious  instruments  of  support. 
The  tibia  and  fibula,  besides  their  shortness,  are  characterized  in  the  Orang  by  the 
greater  space  existing  between  them,  owing  to  the  inward  curve  of  the  tibia,  and  by 
the  rounder  form  of  both  bones.  Both  these  deviations  from  the  human  form,  espe- 
cially the  curvature  of  the  tibia,  are  greater  in  the  Orang  than  in  the  Chimpanzee.  The 
Meckel  have  noticed  a  similar  simplicity  in  the  structure  of  the  hip-joint  in  the  Ornithorhynchus  paradoxus , 
and  I  have  also  found  that  the  same  structure  obtains  in  the  Echidna  Hystrix  and  Ech.  setosa. 
There  can  be  little  doubt  that  the  absence  of  the  ligamentum  teres  is  one  cause  of  the  greater  vacillation  ob- 
served in  the  Orang  Utan,  when  it  attempts  progression  on  the  hinder  legs,  than  in  other  Quadrumana.  In 
Dr.  Abel's  account  Of  the  capture  of  a  very  large  Sumatran  Orang,  it  is  observed,  "  His  motion  on  the  ground 
was  plainly  not  his  natural  mode  of  progression,  for  even  when  assisted  by  his  hands  or  a  stick,  it  was  slow  and 
vacillating;  it  was  necessary  to  see  him  amongst  trees  in  order  to  estimate  his  agility  and  strength."  In 
Audebert's  Histoire  des  Singes,  p.  18,  is  a  note  on  the  progressive  motion  of  the  Orangs,  which  closely  accords 
with  the  structure  above  mentioned ;  it  is  as  follows  :  "  Un  naturaliste  voyageur,  M.  Labillardiere,  qui  a  vu 
de  ces  animaux,  m'a  assure  que  lorsqu'ils  marchent  leurs  jambes  de  derriere  sont  pli4es  en  sorte  que  ce  sont  les 
jambes  de  devants  qui  cheminent."  And  this  account  of  the  use  he  makes  of  his  long  arms  in  progression 
along  the  ground  is  confirmed  by  the  observations  of  M.  Fred.  Cuvier,  who  has  given  some  valuable  obser- 
vations on  the  habits  of  a  living  Orang  Utan  in  the  sixteenth  volume  of  the  '  Annales  du  Museum'.  He  ob- 
serves :  "  Get  Orang-Outang  6toit  enti^rement  conform^  pour  grimper  et  pour  faire  son  habitation  des  arbres. 
En  efFet,  autant  il  grimpoit  avec  facilite,  autant  il  marchoit  p^niblement :  lorsqu'il  vouloit  monter  a  un  arbre 
il  en  empoignoit  le  tronc  et  les  branches  avec  ses  mains  et  avec  ses  pieds,  et  il  ne  se  servoit  que  de  ses  bras,  et 
point  de  ses  cuisses  comme  nous  le  faisons  dans  ce  cas.  II  passoit  facilement  d'un  arbre  a  un  autre  lorsque 
les  branches  de  ces  arbres  se  touchoient,  de  sorte  que  dans  une  for^t  un  peu  ^paisse  U  n'y  auroit  eu  aucune 
raison  pour  que  cet  animal  descendit  jamais  a  terre,  ou  il  marchoit  difBcilement.  En  general  tons  ces  mouve- 
mens  avoient  de  la  lenteur ;  mais  ils  sembloient  ^tre  penibles  lorsqu'il  vouloit  se  transporter  sur  terre  d'un  lieu 
dans  un  autre :  d'abord  il  appuyoit  ses  deux  mains  fermees  sur  le  sol,  se  soulevoit  sur  ses  long  bras,  et  portoit 
son  train  de  derriere  en  avant  en  faisant  passer  ses  pieds  entre  ses  bras  et  en  les  portant  au  dela  des  mains ; 
ensuite  appuye  sur  son  train  de  derrifere  il  avan9oit  la  partie  superieure  de  son  corps,  s'appuyoit  de  nouveau 
sur  ses  poignets,  se  soulevoit  et  recommen9oit  h  porter  en  avant  son  train  de  derrifere  comme  nous  I'avons  dit 
d'abord." 
In  three  living  specimens  of  the  immature  Orang  I  have  witnessed  the  same  debility  of  the  hinder  extremities 
as  instruments  of  support.  If,  however,  the  peculiar  construction  of  the  hip-joint  add  to  the  difficulty  of  pro- 
gression in  the  erect  posture,  arising  from  a  form  of  the  pelvis  and  inferior  extremities  common  to  the  Orang 
with  other  Simia,  it  doubtless  facilitates  his  favourite  mode  of  travelling  among  the  branches  of  his  native 
forests,  by  allowing  a  greater  variety  and  extent  of  motion  to  the  lower  extremities,  and  by  thus  combining,  as 
it  were,  the  peculiar  freedom  of  the  shoulder-joint  with  the  hand-like  form  of  the  foot. 
