366 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 XLVIIL.) 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 tzbia, 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 panedages 5 
and I have also found that the same structure obtains in the Echidna Hystriz 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. Labillardiére, qui a vu 
de ces animaux, m’a assuré que lorsqu’ils marchent leurs jambes de derriere sont pliées 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 Muséum’. He ob- 
serves: “ Cet Orang-Outang étoit entitrement conformé pour grimper et pour faire son habitation des arbres. 
En effet, autant il grimpoit avec facilité, autant il marchoit péniblement: lorsqu’il vouloit monter & 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. I! passoit facilement d’un arbre a un autre lorsque 
les branches de ces arbres se touchoient, de sorte que dans une forét un peu €paisse il n’y auroit eu aucune 
raison pour que cet animal descendit jamais a terre, ov il marchoit difficilement. En général tous ces mouve- 
mens avoient de la lenteur; mais ils sembloient étre pénibles lorsqu’il vouloit se transporter sur terre d’un lieu 
dans un autre: d’abord il appuyoit ses deux mains fermées sur le sol, se soulevoit sur ses long bras, et portoit 
son train de derriére en avant en faisant passer ses pieds entre ses bras et en les portant au dela des mains; 
ensuite appuyé sur son train de derriére il avancoit la partie superieure de son corps, s’appuyoit de nouveau 
sur ses poignets, se soulevoit et recommengoit a porter en avant son train de derriére comme nous l’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 pe/vis and inferior extremities common to the Orang 
with other Simie, 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. 

