486 



GENERAL BIOLOGY 



Distinguishing human characters. The chief features of 

 man's body that distinguish him from his nearest allies are 



precisely those that have 

 favored his great psychic 

 development; his erect at- 

 titude, his hand and his 

 brain. 



Man is the only mammal 

 that stands erect. His legs 

 are longer and stronger and 

 his pelvic bones are stouter 

 and better consolidated to- 

 gether for bearing the entire 

 weight of the body. His 

 arms are shorter and have 

 more freedom of motion at 

 the wrist, and his cranium 

 is better balanced at the 

 top of the vertebral column 

 than in the apes. These 



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using the arms as well as 

 the legs for locomotion. 

 The chief advantage of the erect attitude is that it sets 

 the hands free for other uses. 



The human hand is generalized in structure ; its skeleton 

 is very like that of the foot of a salamander and not far 

 removed from that of the typical vertebrate (compare figures 

 271, 272 and in). It is much like the ape's hand in its 

 opposable thumb and its freedom of rotation at the wrist. 

 These two features make it adaptable to a great variety of 

 uses. Its readiness at grasping and turning make it a 

 splendid servant of the brain ; for it can be used in exam- 

 ining objects, in exploring surfaces and in moving things 



FIG. 271. The framework of the humar 

 hand, a toh. carpal bones; / to 3, bones 

 of the thumb; / to 4, bones of the 

 several fingers. 



