298 ZOOLOGY. 



The salivary glands are placed under the tongue, and con- 

 sist of small masses of little rounded follicles. The saliva is 

 generally thick and sometimes gluish. 



437. There is no velum palati between the mouth and 

 the phanynx. The gullet (Fig. 249), towards the lower part of 

 the neck, communicates with an enlarged pouch called the crop, 

 the walls of which are membranous. In this cavity, which 

 varies much in different birds, the food remains for a time. 

 The crop is most developed in granivorous birds ; it is also 

 found in birds of prey, but it is wanting in the ostrich and in 

 most piscivorous oirds. Below this enlargement the gullet 

 contracts, but soon enlarges to form a second dilatation, called 

 the ventriculus succenturiatus, on the inner surface of which 

 numerous pores may be seen, leading to the follicles which 

 secrete a gastric juice. This second stomach is generally 

 small, but it is larger when the crop is wanting. Finally, 

 this second stomach leads inferiorly into a third, called the 

 gizzard, in which the chymification seems to be finished. 

 This varies in capacity and structure. In flesh-eating birds, 

 the gizzard is thin and membranous ; but in the granivora it 

 is powerfully muscular, and its inner surface is protected by 

 an epidermis almost cartilaginous. Its strength is immense. 



Tongue. 



Fig. 248. Head of the Woodpecker. 



In the ostrich, the hardest substances are acted on by it, and 

 seems to perform the office of a masticatory apparatus. 



The intestine following these stomachs is much shorter 

 than in mammals, but is composed also of two portions. The 

 first, after forming the first turn, winds in various directions ; 

 the second differs but little from the first, and is smooth exter- 

 nally, but is in general easily distinguished from the first by 

 two ctBca or elongated cut de sacs, which exist at its com- 

 mencement. These appendages are very small or absent in 

 birds of prey, but are large in granivorous birds. 



The liver is very large, and fills a great part of the thorax as 



