AVES 



601 



opening called the inferior wnhilicus and at the point where the quill 

 emerges from the skin there is another small opening, the superior 

 umbilicus. In many feathers the hyporachis or after-feather arises 

 from this point. The shaft is often called the rachis. The feathers in 

 many parts of the body are developed in rows with long intervals be- 

 tween the rows in which there are no papillae, but these areas are 

 simply covered over by feathers growing in the adjacent areas. The 

 definite feather areas over the body are called pterylae while the inter- 

 vening featherless areas are apteria (apterylae). 



CEPHALIC 

 PTEIRYLA 

 CERVI CAl_ 

 APTERiUM 

 VE rslTRAU 

 PTERYLA 

 HUME RA1_ 

 PXERYLA 



SPINAL. PT 

 ALAR PT. 



L-ATERAl- 

 AP TE RIUM' 



c'.-vjr'W -J-/ VEN-TRAL. APT. 

 VirtiJ-J.iWT' — FE MORAL. 



CAUDAl. P 

 CRURAl- P 



Fig. 



319. — Diagram showing feather tracts, or pterylae, and featherless areas, or 

 apterylae (apteria) of a rooster. (Drawn by Titus Evans.) 



There is a complete but gradual shedding of the feathers or molt 

 in the fall and a partial one in the spring. Of course, new feathers 

 replace the old as fast as they are shed. There may be some color 

 change of the plumage accompanying the molt. 



Digestive System 



The alimentary canal consists of the principal organs in order: 

 mouth, pharynx, anterior esophagus, crop, posterior esophagus, pro- 

 ventriculus, gizzard (ventriculus), intestine, large intestine, cloaca, 

 anus. The several accessory organs are beak, tongue, salivary glands, 

 liver, and pancreas. The proventriculus and gizzard constitute the 



