66 ARBOREAL MAN 



arboreal grasping-supporting limb. As such, its third 

 segment is still fitted for application to the branches 

 upon the grasp of which its powers of support depend. 

 In conformity with this, its sole is inturned, so that it 

 may be applied to the rounded sides of the branches along 

 which the animal walks. The higher Apes and primitive 

 Man climb up branches with the big toe separated from 

 the other toes, so that the outer side of the foot tends to 

 be applied to one side of the branch, whilst the big toe 

 grasps the other side. In this method of progression the 

 foot is inverted, the soles look inwards, from opposite 

 sides of the branch, towards each other. When the 

 branches are exchanged for the level surface of the earth, 

 this inversion of the foot is a useful adaptation no longer, 

 and in terrestrial bipedal progression a new mechanism 

 is initiated for the eversion of the foot. Into these 

 changes — which are peculiarly human — it is impossible 

 to enter, since they are all finishing touches added after 

 the arboreal habit was abandoned. The eversion of the 

 foot of Man is a post -arboreal develoj^ment, so also is the 

 perfected mechanism for balancing the trunk upon the 

 extended leg; but the extension of the leg upon the trunk, 

 and the anatomical adaptations it involved, are pm'e out- 

 comes of the ordinary evolution of the arboreal habit. 



