The Framework of the Bird 8y 
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 vertebre more distinctly— 
fourteen or fifteen of them. The two deep depressions 
in which the kidneys of the bird were located are also 
Fic. 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 
