132 PHILOSOPHY OF ZOOLOGY. 



ties. On the other hand, the great breadth of his feet, the 

 form of his toes, and the position of the muscles which move 

 them, render them peculiarly calculated, not only for pres- 

 sing the ground to a considerable extent, but embracing 

 some of its inequalities. From the breadth of the pelvis, 

 the legs are placed farther distant in proportion than in the 

 other mammalia, and thus include a more extended base, 

 while the trunk is able to rest upon it more securely. It is 

 owing to these circumstances that the vertical position is 

 easily assumed and maintained by man, while, among qua- 

 drupeds, it is painful. When they do assume it, they in 

 general bend their hind-legs so that their buttocks rest on 

 their heels. 



In Birds, the body> during the position we are now de- 

 scribing, is seldom vertical with respect to the extremities. 

 In some water-fowl, as the grebes, the feet are situated so 

 far behind, and the weight of the body is so great anterior- 

 ly, that they could not stand with the body leaning for- 

 wards, like the generality of birds, without a peculiar ar- 

 rangement of the feet. We accordingly find the body as- 

 suming nearly a vertical position. In some cases where 

 birds stand in this attitude, the tail likewise assists in form- 

 ing a more extended support, by resting on the ground, as 

 may be seen in the cormorant. In some birds, however, 

 as the rail, in which the legs are placed far behind, the 

 toes are uncommonly long, so that the tendency of the fore 

 part of the body to fall to the ground is thus prevented, by 

 the resistance which they offer. The length of the toes, 

 and the manner in which they are disposed, joined to the 

 disposition of the body with regard to its centre of gravity, 

 enable many birds to stand for a great length of time on 

 one foot only, without much exertion. In the stork, " the 

 surface of the femur that articulates with the tibia, has, in 

 its middle, a depression which receives a projection of the 



