524 



ZOOLOGY. 



free barbs, called plumules. Over the tail-bone (coccy.r) are 

 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" 



Pig. 457. Brain of t lie Hen. A , from above, ,, 



B, from below ; a, olfactory bulbs ; b. cere- and Wattles. 

 bral hemispheres; c, optic lobes; (/, cerebel- ^ f,^ i 11 



him ; ci', its lateral parts ; e, medulla. After Ihe Drain IS much larger 

 Carus, from Gegenbaur. , n , n ,-> ,-, 



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- 

 yluvies). 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- 

 ri c end of the stomach in the 

 mammals, is round, with mus- 

 cular walls, especially develop- 

 ed in seed-eating birds, and 



Called the " o-jzzard." In the Fig. 458. Thymus (th} and thyroid 1/1 

 . .. .. . , "lands of a youns; hawk, Buteo viilf/uri* 



fowl the gizzard IS lined With ol Europe;" lr, "trachea. After Gegen- 



a firm horny layer, by which 



the food is crashed and comminuted, thus taking the place 



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



