196 THE VITAL FUNCTIONS. 



of animals; assuming a glandular character, and 

 secreting a watery fluid, which resembles the 

 saliva, both in its sensible and chemical properties. 

 It has been conjectured that many of the vessels, 

 which are attached to the upper portion of the 

 alimentary canal of insects, and have been termed 

 hepatic, may, in fact, prepare a fluid having more 

 of the qualities of the pancreatic than of the biliary 

 secretion.* 



The alimentary canal of fishes is in general 

 characterized by being short; and the continuity 

 of the stomach with the intestines is often such as 

 to offer no well marked line of distinction between 

 them. The caeca are generally large and numerous; 

 and a number of tubular organs, connected more 

 especially with the pylorus, and called therefore 

 the pyloric appendices, are frequently met with, re- 

 sembling a cluster of worms, and having some 

 analogy, in situation at least, and probably also in 

 their functions, to the hepatic or pancreatic vessels 

 of insects. Their appearance in the Salmon is 

 represented at p, in Fig. 331. The pancreas itself 

 is only met with, in this class of 

 animals, in the order of cartilaginous 

 fishes, and more especially in the 

 I^ay and the Shark tribes. A dis- 

 tinct gall-bladder, or reservoir, is also 

 met with in some kinds offish, but 

 is by no means general in that class. 

 In the classes both of Fishes and of Reptiles, 

 which are cold-blooded animals, the processes of 

 digestion are conducted more slowly than in the 



* Ciliary motions have been discovered by Purkinje and Valentin 

 in the alimentary canals of many of the Mollusca. 



