GASTEIC GLASDS. 



183 



332. The form of the small intestine is less variable than 

 that of the stomach. It is a narrow tube with thin walls, coiled 



Fig. 186. 

 B 



Fig. 186. B, glands 

 of the proventriculus of 

 different birds ; o, of the 

 peacock (Pavo crista- 

 tus). b, of the Cathar- 

 tes percnopterus. c, of 

 Casuarius galeatus. d, 

 of Falcopygargus. e, of 

 the fowl. /, of the os- 

 trich. After Home, 

 Lecture on Comp. Anat. 

 ii. pi. 5G. 



in various directions in the vertebrate animals (fig. 180), but 

 more simple in the invertebrate, especially the insects (fig. 1 79), 

 Its length varies according to the nature of the food, being in 

 ral longer in herbivorous than in carnivorous animals. 

 In this portion of the canal, the aliment undergoes its com- 

 plete elaboration, through the agency of certain juices which 

 here mingle with the chyme, such as the bile secreted by the 

 liver, and the pancreatic juice secreted by the pancreas. The 

 result of this elaboration is to produce a complete separation 

 of the truly nutritious parts, in the form of a milky liquid 

 called chyle. The process is called chylification ; and there 

 are great numbers of animals, as insects, crabs, lobsters, some 

 worms, and most of the mollusca, in which the product of 



