130 ERECT ATTITUDE. 



which the weight of the body has to bend the leg in stand- 

 ing. The muscles of the calves lift the heels, and thereby 

 elevate the whole body, which is supported on the astraga- 

 lus : the weight is tlius maintained on the anterior part of 

 the feet; and tlie individual is said to stand on tiptoes. If 

 the foot of one side be lifted from the ground, and the op- 

 posite heel be raised by the calf of its own side, the whole 

 body is then elevated by the muscles of one calf. When a 

 person stands on tiptoe with a burden on the shoulders, or 

 on any other part of the trunk, the weight of this, as well 

 as of the body, must be raised and supported by the mus- 

 cles of the calf. In running, leaping, jumping in the air, 

 dancing, &c. the projection of the body is accomplished by 

 the same power. 



Aristotle, and others after him, have justly observed, 

 that calves of the legs can be ascribed to man only. 



The whole arrangement of the thorax corresponds to the 

 erect attitude of man. It is flattened anteriorly, possesses a 

 very broad sternum, is wide transversely, but shallow from 

 before backwards. Its lateral width and inconsiderable 

 depth from sternum to spine, not only throw the arms far 

 apart, and thus give a more extensive range to their motions, 

 but diminish that preponderance of the trunk towards the 

 front, which, although it is unimportant in the horizontal, 

 is very inconvenient in the erect attitude. Man is said to 

 be the only animal in which the transverse exceeds the an- 

 tero-posterior diameter of the chest. Even in the simia 

 satyrus the latter exceeds the former measurement *. 



The human sternum is short, as well as broad ; hence a 

 large space is left between the front of the chest and the 

 pelvis, unprovided with bony supports ; the weight of the 

 viscera, which are sufficiently guarded by the abdominal- 

 muscles, is securely sustained below by the ample pelvis. 



Quadrupeds have a thorax compressed laterally, narrow 

 and keel-shaped on its sternal aspect, consequently deep 

 from sternum to spine, but confined in the transverse di- 

 mension. This structure, with the absence of clavicles, al^ 



* Camper, ffiwyrcs, 1. p. 115, 



