DIGESTIVE APPARATUS OF BIRDS. 381 



very soft ; in most granivorous Birds it is dry, triangular, and 

 beset towards the base with small cartilaginous points ; and in 

 some insectivorous Birds, its extremity is armed with hooks 



Tongue. 



FIG. 200. SKULL OF WOODPECKER. 



or is jagged. The salivary glands are placed under the tongue, 

 and consist of a mass of small rounded follicles ; the saliva is 

 generally thick ; and sometimes it is quite glutinous. 



344. The Pharynx is not separated from the mouth by a 

 movable partition, as in the Mammalia ; and has no peculiarities. 

 The (Esophagus (Fig. 201) beginning at the inferior part of the 

 neck, communicates with the first digestive cavity named the 

 crop ; the sides of which are membranous. The food remains 

 for a certain time in this first stomach, whose form and size 

 vary. It is in the granivorous Birds, that the crop is most 

 developed ; it is also found in Birds of Prey; but it is wanting 

 in the Ostrich, and in most Birds that feed on Fish. Below 

 this part the (Esophagus is again contracted, and presents 

 further down a second dilatation, called the ventriculus succen- 

 turiatus, whose internal surface is perforated by a considerable 

 number of small pores, communicating with follicles that secrete 

 the gastric juice ; in general, the size of the stomach is small ; 

 but in Birds deficient in the crop it is larger than usual, and 

 seems to take the place of it. The ventriculus succenturialus 

 opens below into a third stomach named the gizzard; in which 

 the process of chymification is completed. This varies much in 

 capacity; but it is particularly in the structure of its walls, that 

 important differences appear. In Birds that feed on flesh only, 

 the sides of the gizzard are thin and membranous ; but in those 

 that swallow food, which is harder and more difficult to digest, 

 it is furnished with strong muscles, intended to compress 



