90 THE VITAL FUNCTIONS. 



gram 1 shall make frequent reference in the fol- 

 lowing description of this system. 



The food is, in the first place, prepared for di- 

 gestion by several mechanical operations, which 

 loosen its texture and destroy its cohesion. 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 muscular tube, called the (Esophagus, (repre- 

 sented in the diagram by the letter o,) into the sto- 

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

 cai'dia. 



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 far- 

 ther subjected to the action of several fluid secre- 

 tions, 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, which are exceed- 

 ingly numerous, are spread over the inner surface 

 of the intestines, whence they absorb, or drink up 

 the chyle. They may be compared to internal 

 roots, which unite as they ascend along the mesen- 

 terij (m), or membrane connecting the intestines 

 with the back ; forming larger and larger trunks, 



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