524 



zooLoar. 



free barbs, called plamules. Over the tail-ljonc {coccyx) are 

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



bird in oilino- and dress- 



Fig. 457.— Brain of the Hen 

 7?, from lic'low ; rt, olf^ictory bulbs ; b, cere- 

 bral hemisplieres; c, optic lobes; d, cerebel- 

 lum : d', Us lateral parts ; <?, medulla.— After 

 Carus, from Uegeiibaur. 



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 

 cereliral 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- 

 (jluvies). The stomach is di- 

 vided into two parts, the first, 

 the provcntriculus, 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 birds, and 

 called the "gizzard." In the 

 fowl the gizzard is lined with 

 a firm horny layer, by which 

 the food is crushed and comminuted, thus taking the place 

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



Fig. 458.— Thymus (WO and thyroid (0 

 glands of a younji; hawk, Buleo vulgaris 

 of Europe ; U\ trachea.— After Gegen- 

 baur. 



