524 



ZOOLOGY. 



Fig. 457. — Brain of the Hen. A. from above, 

 5, from below ; a, olfactory bnlbs ; b. cere- 

 bral hemispheres ; e, optic lobes ; d. cerebel- 

 lum ; d'. Its lateral parts ; e, medulla. — After 

 Cams, from Gegenbanr. 



free barbs, called plumules. Over the tail-bone {coccyx) ara 

 usually sebaceous glands, which secrete an oil, used by the- 



bird in oiling and dress- 

 ing or "preening" its 

 feathers. In some birds, 

 especially in the males of 

 the gallinaceous fowls, as 

 the cock and turkey, the 

 head and neck are orna- 

 mented with naked folds 

 of the skin called • ■ combs" 

 and ''wattles.'" 



The brain is much larger 

 than in the reptiles, the 

 cerebral hemispheres being greatly increased in size, while- 

 the cerebellum is transversely furrowed, and is so large as to 

 cover the whole of the me- 

 dulla. The alimentary tract 

 consists of an oesophagus as 

 long as the neck ; it dilates 

 in the domestic fowl and other 

 seed-eating birds, as well as 

 in the raptorial birds, into a 

 lateral sac called the crop {in- 

 gluvies). The stomach is di- 

 vided into two parts, the first, 

 the proventriculus, which is 

 glandular, secreting a digest- 

 ive fluid ; and the second, 

 which corresponds to the pylo- 

 ric end of the stomach in the 

 mammals, is round, with mus- 

 cular walls, especially develop- 

 ed in seed-eating binls, and 



called the "gizzard."' In the Ffe. 458.— Thymns {«) and thyroid m 

 • 1 .1 . J ■ T J „-j-i, elands of a young hawk, Buteo vulgarii- 



fowl the gizzard is lined with or Earope ; tr, trachea—After G^n- 



a firm homy layer, by which 



the food is crashed and comminuted, thus taking the place- 



of teeth. The intestine (including the large and small intes^ 



