SKELETON OF BIRDS. 507 



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-bone ;" the 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- 



cles// are united together 



where they join the ster- 



num, to form the fork- 



like bone known as the 



" 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- 



,, ~, ,. Fig. 250. BONES OF THE SHOULDER AND 



pable 01 attorning to the BREAST OF BIRDS. 



drawing-together of the 0;Scapu]a; c , coracoid bone; /? claviclesunited 



Shoulder- JOintS by the at their junction with the summit of the keel 



nf fho vkonfnval b of the sternum s, which is connected with 

 Ot tne ectOial 



the ribs by the ossified costal cartilages co. 



muscles. The bones of 



the pinion consist of the humerus (fig. 249, A), 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, 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 ( 755). 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 



