AVES 



611 



ends of the coracoids and fuse with each other ventrally to form the 

 "wishbone" or "collar bone." The wing is a greatly modified front 

 limb, but strictly homologous to the arm. There is a humerus in the 

 upper arm whose head fits in the glenoid cavity. The radius and ulna 

 support the forearm. The carpus or wrist is composed of two bones, 

 scapholunar and cuneiform, followed by two metacarpals. The first 

 digit or pollex has only one phalanx or joint, the second has two 

 phalanges, and the third is located at the end of the metacarpal bone. 



SARTORIUS 



GLUTEUS PRIMUS 



SEMITENDINOSUS 



GASTROCNEMIUS 



FLEXOR PERFORATUS 

 INDICIS SECUNDUS 

 PEDIS 



FLEXOR PERFORATUS 

 MEDIUS SECUNDUS 



PERONEUS LONGUS 



Fig. 326. — Lateral view of tlie muscles of the hind leg of the chicken. (Drawn by 



Titus Evans.) 



The pelvic girdle is fused quite rigidly to the sacrum. The ilium, 

 ischium, and pulis of each side are closely fused with each other. 

 The pelvic limb fits into the rounded concavity on each side of the 

 girdle. This socket is called the acetabulum. The hindlimb supports 

 the body in nearly an upright position when the bird is walking. The 



