DIGESTIVE OEGANS. 



191 



five or six days. In the swelling under the throat, called the 

 crop, a (Fig. 68), or first stomach, which is largely developed in 

 some of the granivorous or grain- eating birds, the food remains 

 for a time, where it undergoes certain modifications which 

 facilitate digestion ; thence it passes into the succenteric ventricle, 

 or second stomach, b (Fig. 68), there it imbibes the necessary 

 amount of gastric juice ; being finally transformed into chyme in 

 the gizzard, c (Fig. 68), or third stomach, 

 which is possessed of great muscular power, 

 being capable of acting upon the most solid 

 bodies, triturating even the flints and gravel 

 which the gallinaceous birds swallow to aid 

 their digestion. 



It is a curious fact that a grain of seed, 

 introduced into the stomach, may be digested 

 without alteration, and ejected where it will 

 germinate, if it meets with no obstacle to its 

 vegetation. In this manner trees are fre- 

 quently found in regions where their species 

 appear to have been previously unknown. 



Chyle, which is a milky fluid formed from 

 the junction of chyme and bile, is received 

 by the small intestine, where the bile also 

 flows from the liver and the saliva from the 

 pancreas. 



The urinary apparatus consists of the kid- 

 neys, two in number, thick and irregular, and distinct one from 

 the other, abutting on the intestine, which terminates in a species 

 of pouch, or cloaca, through which evacuation, alternately of urine, 

 excrement, and eggs, takes place. 



The sense of touch, of smell, of taste, and hearing are only 

 slightly developed in birds. Some have spoken of great deli- 

 cacy of scent in birds of prey, which are observed to assemble in 

 great numbers on fields of battle and other places where human 

 carcasses are exposed. But the opinions of naturalists, such as 

 Audubon and Levaillant, seem to prove that these animals were 

 attracted rather by the sight than smell. 



The organ of sight is, indeed, more highly developed in birds 



