THE BIRD'S SKELETON 



293 



The hind limbs of the bird represent more modifications and a 

 greater number of bones. The tibia is the principal bone, while 

 the most noticeable characteristic is the fused tarsus and meta- 



FIG. 141. Skeleton of fowl. 1, Upper jaw; 2, lower jaw; 3, nasal cavity; 4, eye cavity; 

 5, skull; 6, neck vertebrae; 7, scapula; 8, clavicles (wish bone); 9, digits; 10, bones of fore- 

 wing; 11, ulna; 12, radius; 13, humerus; 14, backbone; 15, ribs; 16, femur; 17, acetabulum; 

 18, ischium; 19, pygostyle or tail bones; 20, breastbone or sternum; 21, tibia; 22, tarso- 

 metarsus; 23, spur; 24, rear toe; 25, toes. 



tarsus. The thigh bones are exceedingly short, and when the 

 bird is in full plumage are never seen. The fowl normally has only 

 four toes. The fifth one is missing. (The Dorking and Houdan 



