74 ARBOREAL MAN 



There was a period in zoological literature when dis- 

 cussion was waged earnestly, and without satisfaction, 

 as to what should be called a hand and what a foot. 

 The hand and the foot are alike in some animals; they 

 are quadrupedal or quadrumanous, but some exhibit 

 differences in the structure of the third segment of the 

 fore and hind limbs. The point in dispute was the exact 

 stage at which differentiation in a quadrumanous animal 

 produced a hand and a foot. In this academic discussion 

 Etienne Geoffi'oy St. Hillaire, Huxley, Owen, and many 

 others took their part. We may say, however, that the 

 problem as it was presented did not offer any very special 

 difficulty beyond the determination of the function of the 

 member. This was the solution which Huxley recognized 

 at once, and to which he always adhered. The Anthro- 

 poids have hands and feet, and their hands and feet are 

 differentiated by their function. We will accept such 

 a solution, and assume that we understand perfectly well 

 what we mean when we speak of a Gorilla's foot. That 

 is a simple way out of the dilemma, but we must recognize 

 it does not do away witli the difficulty whicli presents 

 itself the moment we attempt to differentiate between 

 a hand and a foot from the point of view of structure. 

 A monkey's foot is a definite thing; it has a definite 

 function which distinguishes it from the hand (see Fig. 27). 

 The same applies with even more force to the case of an 

 Anthropoid, but the hand and foot in these animals are, 

 anatomically, remarkably similar structures in many 

 ways. The specialization of the foot as a supporting 

 organ is carried to very definite lengths in the Anthro- 

 poids; in the Gorilla is seen the best foot developed 

 among the Giant Apes. We will therefore take this foot 

 as an anatomical illustration of the stage of development 

 to which foot differentiation is carried in existing Primates. 

 The foot of a Gorilla differs from the hand in the fact 

 that all the digits are placed nearer to the extremity of 

 the thii'd segment of the hind limb; there is a greater 



