LESSONS IN ZOOLOGY. 301 



cervical region, a short, slightly flexible, caudal region and a 

 rigid dorsal lumbar and sacral region. 



The ribs join the broad sternum forming a deep conical body 

 cavity, whose walls are an excellent foundation for a strong 

 shoulder joint. The clavicles unite so as to form an arch or fork, 

 then the scapula and coracoid wedged in between the rigid ver- 

 tebrae and the heavy sternum, making a socket for the broad 

 faced humerus that gives the bird one of the best of shoulder joints. 

 The wing is completed by the ulna and radius, and by the more 

 or less modified parts of the wrist and hand. 



The foundation for the articulation of the legs consists of an 

 elongated pelvis made up of the lumbar and sacral vertebrae 

 fused with the long iliac bones and the shorter ischial and pubic 

 bones, The acetabular cavity is deep and the joint is firm. The 

 short, heavy femur is concealed within the body, the knee joint 

 usually being just at the surface of the body. The first free por- 

 tion of the leg is composed of the tibia, the fibula being rudimen- 

 tary; the second portion is a fusion of tarsal and metatarsal 

 bones, which lead to the phalanges. 



The muscular system is well developed and especially adapted 

 to quick, vigorous movements. The skin is covered with feathers 

 which correspond to the hair of the mammalia. A feather has a 

 shaft and vane and the vane is made up of barbs and barbules. 

 Feathers from different parts of the body vary considerably in 

 appearance and use. Feathers are usually imbedded in the skin, 

 but the larger stiffer feathers of the wing, called quills, are inserted 

 in the bones of the wing. 



The quills on the hand are the primaries, those on the forearm 

 are secondaries, and when found on the arm they are tertiaries. 

 The skin on the legs and toes is usually covered with horny scales 

 or plates. 



The nervous system and the sense organs are well developed. 

 The alimentary canal consists of the mouth with the salivary 

 glands, the oesophagus, crop, pro-stomach, stomach or gizzard, 

 and the intestine with the pancreas and liver. The kidneys and 

 the ovaries evacuate through the intestine. The heart and the 



