84 THE STRUCTURE OF MAN 



to the upright gait, becomes longer than the internal or tibial 

 (c.*.) ; and also how the astragalus (as.} and calcaneum (cZ.) which 

 originally slope laterally outwards, shift inwards, i.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 



FIG. 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 

 limbs ; 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 foetal life), and 



