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, im 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, jomed 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 
