SKELETON OF BIRDS. 
607 
attached the muscles that raise the wings, is very narrow in 
Birds, in accordance with their small demand for muscular 
power in this direction. This narrow scapula forms one part 
of what is known as the “ side-bonethe other part c of 
which is formed by a bone termed the coracoid, that is only 
represented in Man and other Mammals by the short coracoid 
process of the scapula 
(§ 635). The two clavi- 0 
cles//are united together 
where they join the ster¬ 
num, to form the fork¬ 
like bone known as the 
u merry - thought,” the 
strength of which, like 
the projection of the keel 
of the sternum, serves 
to indicate the power of 
flight, by the degree of 
resistance which it is ca¬ 
pable of affording to the 
drawing-together of the 
shoulder-joints by the 
action of the pectoral 
muscles. The bones of 
the pinion consist of the humerus (fig. 249, Ji), the two bones 
of the fore-arm o, the bones of the wrist ca (which are here 
scarcely developed), and the bones of the fingers ph y each 
joint of which shows indications of being made up of two or 
three separate bones united together. In no bird are these 
bones ever separated into distinct fingers, since they are never 
required for any other purpose than that of supporting the 
wing-feathers.—The leg is connected with the spinal column 
by a pelvis, of which the iliac bones are greatly lengthened 
and firmly attached to the spine, but which is not completed 
into a ring by the junction of the bones in front, as in Mam¬ 
mals ; such a completion would have prevented the passage 
of the bulky eggs deposited by these animals (§ 7 55). In the 
hinder extremity we find the femur or thigh-bone (principally 
concealed in the figure by the bones of the wing), the two 
bones of the leg t, which are commonly united in part of their 
length, the shank or ancle-bones ta , which are peculiarly 
Fig. 250. —Bones of the Shoulder and- 
Breast of Birds. 
o, scapula; c, coracoid bone; /, clavicles united' 
at their junction with the summit of the keel 
b of the sternum s, which is connected with 
the ribs by the ossified costal cartilages co. 
