THE ANIMAL, MAN (ANTHROPOLOGY) 



543 



Skeleton of a hippopotamus, showiiif;: the anti- 

 clinal arrangement of \ ertebral spines character- 

 istic of quadrupeds, but not of bipeds. (After 

 Hesse.) 



At the other end of the spinal column the tail bones, no longer 

 useful in any of the former ways, telescoped together to form the 

 coccyx. This fusion of 

 the caudal vertebrae 

 formed a mass which bent 

 in and became embedded 

 under the skin, forming 

 a part of the floor of the 

 pelvic basin, now a neces- 

 sary underpinning for the 

 support of the shifting 

 visceral weight. So it 

 came about that man in 

 tucking his ancestral tail 



between his legs turned this apologetic performance to advantage. 

 The thorax with its encircling ribs became flattened and widened 

 as a consequence of upright posture, while the sternal bones, relieved 

 from visceral weight, became firmly fused together and shortened, 

 allowing more freedom and effectiveness of motion for the respiratory 

 muscles. 



The legs of man straightened, with a greater resultant efficiency 

 in leverage, leaving the arms relatively shorter, since, with the passing 

 of locomotion on all fours, legs and arms no longer needed to be 



of the same approximate 

 length. 



The human foot met 

 its new responsibilities in 

 a variety of adaptable 

 ways. Being squarely 

 plantigrade on the ground, 

 the bones involved be- 

 came arranged in two 

 arches, one longitudinal 

 and one transverse, to 

 provide sprightliness to 

 the gait, as well as an ade- 

 quate support to body-weight. One of the ankle bones, the calcaneus, 

 projected out behind forming a heel, thus lessening the likelihood 

 that the balancing biped might tend to tip over backward. In the 

 hind foot of a quadruped such a development of a heel was unneces- 



The two arches of the human foot. (From 

 Walter, The Unman Skeleton. By permission of 

 The Macmillan Company, publishers.) 



