THE EVOLUTION OF THE HUMAN" FOOT. 



'06i 



Fig. 12. — Skeleton of the foot (inferior surface). I, Gorilla. 

 II, Negro. Ill, European, r, Calcaneum; av, Anatomical 

 a.xis (to show the deviation of the calcaneum i. 



foot, this lesser process is set very low, l)eing almost u continuation of 

 the inferior surface of the calcaneum. The development of the arch 

 in man had for its first eti'ect the raising of this lesser process and then 

 a reduction of its dimensions, the astragalus resting directly on the 

 bod}^ of the calcaneum because of the approach of the latter to the 

 anatomical axis" of the foot. This approach is, in fact, another char- 

 acter that varies with the 

 development of the arch. 

 In the anthropoids the heel 

 is pushed strongly outward ; 

 in European man its axis 

 coincides with the anatom- 

 ical axis of the foot, and 

 thus attains the position 

 mentioned above and rep- 

 resented in figure 12. 



Corresponding with the 

 inverted position of the 

 foot, the axis of the poste- 

 rior surface of the calca- 

 neum is in tree dwellers 

 oblique from above downward and from without inward. As the arch 

 becomes more completely formed, this axis becomes more and more 

 perpendicular to the ground. It is not jet quite vertical in the Aus- 

 tralian, but is so in the European. Men of the inferior races and 

 new-born children have in this respect a position between the gorilla 

 a id the European adult, and in the arrangement of the diti'erent ele- 

 ments of the foot all is so 

 well correlated that this 

 deviation, more marked in 

 anthropoids than in other 

 apes, varies as does the 

 divergence of the head of 

 the astragalus, which is 

 itself controlled b}^ the 

 ^ fn^edom of movement of 



^rjffh/m/////////////////////)///PJ////// the first toe, another char- 



F.G. 13.-Skck-ton of the foot and lmv_cr leg, showing the ^^^^, ^^ adaptation to arbo- 

 torsion of the heel. I, Gorilla. II, European. 1, Calca- _ i 



neum; 2, Astragalus; 3, Tibia; 4, Fibula. real life. 



The adaptation of the arboreal foot to plantigrade walking and the 

 development of the arch among the arboreals, also produced moditica- 

 tions in the astragalus both as to its position and to its form; we will 



« The anatomical axis of tlie foot is the exact bisector of the angle C, correspond- 

 ing nearly to the line which joins the middle of the posterior snrface of thecalcaneuni 

 witli the space between' the first and second toes. 



