260 NATURAL HISTORY. 



foot in its natural condition, uncramped by artificial 

 coverings, have some power of using the great toe as- 

 a hinder thumb. This is exemplified in many sailors, 

 and in various savage tribes; and in such cases the 

 prehensile great toe is of much assistance in climbing. 

 It is also well-known that in individuals who have never 

 possessed, or who have lost the use of the hands, the 

 great toe can be trained by constant use to act as a 

 thumb, and the foot can thus be converted into a more 

 or less efficient hand. Suppose, however, that in some 

 particular region, circumstances should arise which should 

 render it advantageous or necessary for men to quit 

 the ground, and to take up their abode permanently 

 in trees. Such circumstances can be quite easily 

 imagined. In such a case, it would be of enormous 

 advantage to the individual that he should be able to 

 use his great toe in grasping, so as to help him in 

 climbing. We may assume, therefore, that each individual 

 would practise himself, consciously or unconsciously, in 

 using his feet as prehensile organs. We may also assume 

 that each individual would in the course of time succeed 

 in these prolonged attempts, and would ultimately acquire 

 a more or less complete power of 'opposing' the great 

 toe to the other digits, and so of using the foot to grasp 

 branches in climbing. Supposing, however, that the 

 conditions which drove men to reside in trees became 

 permanent, we cannot doubt that in each successive 

 generation this power of using the foot in grasping 

 would improve. We may rest assured that repeated 

 efforts to perform a particular function with a particular 

 organ must result in an increased ability on the part 



