84 THE STRUCTURE OF MAN 
to the upright gait, becomes longer than the internal or tibial 
(c.t.); and also how the astragalus (as.) and caleaneum (cel.) which 
originally slope laterally outwards, shift inwards, 2.e. towards the 
pre-axial side, so that they come more into a line with the long 
axis of the tibia. 
The above-described modifications find a parallel in certain — 
most important changes which the foot itself is even now under- 
going. To understand these rightly we must enter somewhat into 
detail, in order to gain an insight into the primitive history of 
the human foot. 
Thanks to Comparative Anatomy and Development, we have 
C 
Fic. 59.—THE Upper ANKLE-JOINT, POSTERIOR ASPECT. 
A, adult Chimpanzee ; B, Australian native ; C, Caucasian, to show the increasing length 
of the malleolus fibularis (c.f), and the difference in the position of the astragalus 
(as.) and calcaneum (cl.) in relation to the long axis of the tibia, in passing from 
the lower to the higher type. 
obtained a sufficiently correct estimate of the skeleton of the 
limbs in general, to grasp the essential points in the plan of 
structure common to the hand and foot. The fact that there are 
obstacles in the way of obtaining a perfectly clear insight into 
this matter need not surprise us, when we take into account the 
long series of adaptations which have resulted in the human 
lmbs; indeed, we can no longer expect to find the primitive condi- 
tion retained in either the fore- or the hind-limb. If the fore-limb 
has been transformed from an ambulatory to a prehensile organ, 
the hind-limb has already reached a third stage in progressive 
modification—as, having first served for support and locomotion, 
it next became transformed into a grasping organ (as is proved 
by the musculature of the sole of the foot, and by the Ape-like 
apposable condition of the great toe during fcetal life), and 
