ORGANS OF DIGESTION. 21 



30. Below the crop, the cesophagus becomes narrow and enters 

 the thorax. Soon after entering the thorax it again dilates to 

 form the second stomach, called proventriculus, or bulbus glandu- 

 losus. This cavity is remarkable for the great number of follicles 

 which are lodged in the thickness of its parietes, and which secrete 

 an acid liquid (the gastric juice) designed to effect digestion. This 

 ventricle is much larger, and more numerously supplied with 

 glands, in those birds that have no crop, than in those that are 

 provided with it. Internally, it opens into a third stomach, the 

 gizzard, which is of a globular form, and varies in structure ac- 

 cording to the diet or food of these animals. In granivorous 

 birds its muscular parietes are very thick and strong, and it is 

 lined inside by a kind of thick, hard epidermis which resembles 

 horn ; in diurnal birds of prey, on the contrary, it is very thin, 

 and in some aquatic birds, such as Herons and Pelicans, it forms 

 but a single sack with the second stomach. 



31. The intestines of birds are not so long, generally, as those 

 of the mammalia ; in most of these animals they are only two 

 or three times the length of the body. The intestinal canal is 

 divided into two portions, namely, the small and the large intes- 

 tine, and near the anus, it has two appendices, terminating in cul- 

 de-sacs, called ccBcums. 



32. The small intestine communicates with the gizzard by the 

 opening of the pylorus, which is situate very near the cardia, 

 and is without valves. The bile is poured into this intestine by 

 two ducts, which alternate with two or three canals, through 

 which passes the pancreatic juice. 



33. The secreting organ of the bile, the liver, is generally more 

 voluminous than in mammals, and is divided into two nearly 

 equal lobes. The gall-bladder is ordinarily large, but in some 

 birds, such as the Parrot, it is entirely wanting. 



34. The pancreas are also large, and are found in the first 

 fold formed by the intestine, 



35. The cceciims vary much in length ; in the granivorous, and 

 omnivorous birds, they are generally thick and long; they are 

 wanting in most of the diurnal birds of prey, but in the nocturnal 

 birds of prey, they are, on the contrary, very large, 



30. What constitutes the second stomach or ventricle in birds ? What is 

 the gizzard ? Are the gizzards of all birds alike? 



31. What is the length of the intestinal canal in birds ? How is it divided ? 



32. How does the bile enter the small intestine 7 



33. Is the gall bladder found in all birds ? 



34. Where are the pancreas situated ? 



35. Are the ccECums generally of the same size ? Are they always present 

 in birds? 



