VERTEBRATES: BACKBONE AND BRAIN 93 



ally not opposable. The muscles of the leg are heavy 

 aiid the knee-joint has a very broad articulating sur- 

 face. But the great result of man's erect posture is 

 that the hand is set free from the work of locomotion, 

 and has become a delicate tactile and tool-using organ. 

 The importance of this change we cannot over-estimate. 

 The hand was the servant of the brain for trying all ex- 

 periments. Had not our arboreal ancestors developed 

 the hand for us we could never have invented tools nor 

 used them if invented. And its reflex influence in de- 

 veloping the brain has been enormous. The arm is 

 shorter and the hand smaller. The brain is absolute- 

 ly and relatively large, and its surface greatly convo- 

 luted. This gives place for a large amount of " gray 

 matter," whose functions are perception, thought, and 

 will. For this gray matter forms a layer on the out- 

 side of the brain. 



Thus, even anatomically, man differs from the an- 

 thropoid apes. His whole structure is moulded to and 

 by the higher mental powers, so that he is the "An- 

 thropos ' of the old Greek philosophers, the being 

 who " turns his face upward." Yet in all these ana- 

 tomical respects some of the apes differ less from him 

 than from the lower apes or " half apes." And every 

 one of these can easily be explained as the result of 

 progressive development and modification. Whoever 

 will deny the possibility or probability of man's de- 

 velopment from some lower form must argue on psy- 

 chological, not on anatomical, grounds ; and it grows 

 clearer every day that even the former but poorly 

 justify such a denial. 



But it is interesting to note that no one ape most 

 closely approaches man in all anatomical respects. 



