COMPLEX APPARATUS FOR NUTRITION. 107 



this diagram I shall make frequent reference in 

 the following description of this system. 



The food is, in the first place, prepared for 

 digestion by several mechanical operations, 

 which loosen its texture and destroy its cohe- 

 sion. It is torn asunder and broken down by 

 the action of the jaws and of the teeth; and it 

 is, at the same time, softened by an admixture 

 with the fluid secretions of the mouth. It is 

 then collected into a mass, by the action of the 

 muscles of the cheek and tongue, and swallowed 

 by the regulated contractions of the different 

 parts of the throat. It now passes along a mus- 

 cular tube, called the (Esophagus, (represented 

 in the diagram by the letter o,) into the stomach 

 (s), of which the entrance (c;) is called the 

 cardia. 



In the stomach the food is made to undergo 

 various chemical changes ; after which it is con- 

 ducted through the aperture termed the pylorus 

 (p), into the canal of the intestine (i i), where it 

 is further subjected to the action of several fluid 

 secretions derived from large glandular organs 

 situated in the neighbourhood, as the liver (l) 

 and the pancreas ; and elaborated into the fluid 

 which is termed Chyle. 



The Chyle is taken up by a particular set of 

 vessels, called the Lacteals, which transmit it to 

 the heart (h). These vessels are exceedingly 

 numerous, and arise by open orifices from the 



