The Framework of the Bird 89 



way to locate these is first to find the socket in which 

 fits the head of the thigh-bone. This is the deep cup- 

 shaped depression on each side, and all three bones join 

 in making the socket. The ilium lies along the back 

 and forms a sort of roof over the portion of the back- 

 bone in this region. If we look at the under side of this 

 bone, we may see the fused vertebrae more distinctly 

 fourteen or fifteen of them. The two deep depressions 

 in which the kidneys of the bird were located are also 



FIG. 62. Pelvic girdle of a bird. 



now visible. As the coracoid is the great pivot of the 

 wing, so the ilium helps most to bear the strain of hop- 

 ping and running. In the frog, which progresses by 

 hops or great leaps, the ilium is also largely developed; 

 indeed we can see it through the skin, thus giving the 

 broken-back appearance to that creature. 



Each side of the thigh-bone box is formed by the ischium, 

 which is closely fused with the ilium except in most of 

 the ostrich-like birds, the tinamous, and in reptiles, 

 where these bones are free throughout their entire length. 

 We can readily make out the pubis as a slender bar of 



