DIGESTION. 



135 



mucous glands, and they are often constructed so as to 

 pour their contents into intermediate cavities, or small sacs, 

 which are denominated follicles, where the fluid is collected 

 before it is discharged into the cavity of the stomach. The 

 gastric glands of birds are larger and more conspicuous than 

 those of quadrupeds: but, independently of those which are 

 situated in the stomach, there is likewise found, in almost 

 all birds, at the lo\ver termination of the oesophagus, a large 

 glandular organ, which has been termed the bulbulus glan- 

 dulosus. In the Ostrich, this organ is of so great a size as 

 to give it the appearance of a separate stomach. A view of 

 the internal surface of the stomach of the African ostrich is 

 given in Fig. 302; where c is the cardiac cavity, the coats 



302 



of which are studded with numerous glands; G, G, are the 

 two sides of the gizzard. Fig. 303 shows one of the gas- 

 tric glands of the African ostrich; Fig. 304, a gland from 

 the stomach of the American ostrich, and Fig. 305, a sec- 

 tion of a gastric gland in the beaver, showing the branching 

 of the ducts, which form three internal openings. In birds 

 that live on vegetable food, the structure of the gastric 

 glands is evidently different from that of the corresponding 

 glands in predaceous birds; but as these anatomical details 

 have not as yet tended to elucidate in any degree the pur- 



