S2 THE VITAL rUXCTIOXS. 



lowed by the regulated contractions of the different parts of 

 the throat. It now passes along a muscular tube, called 

 the Oesophagus, (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 che- 

 mical changes; after which it is conducted through the aper- 

 ture termed the pi/lninis (r,) into the canal of the intestine 

 (i I,) where it is farther subjected to the action of several 

 fluid secretions derived from large glandular organs situated 

 in the neiglil)ourhood, 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 Lacleals, which transmit it to the heart (ii.) These 

 vessels are exceedingly numerous, and arise by open orifices 

 from the inner surface of the intestines, whence they ab- 

 sorb, or drink up the chyle. They may be compared to 

 internal roots, which unite as they ascend along the mesen- 

 tery (m,) or membrane connecting the intestines with the 

 back; forming larger and larger trunks, till they terminate 

 in an intermediate reservoir (r,) which has been named the 

 Ixeccptacic of the Chyle. From this receptacle there pro- 

 ceeds a tube, which, from its passing through the thorax, is 

 called the Thoracic duct (t;) it ascends along the side of 

 the spine, which protects it from compression, and opens 

 at V, into the large veins which are pouring their contents 

 into tlie auricle, or first cavity of the heart (u.) whence it 

 immediately passes into the ventricle, or second cavity of 

 that organ (ii.) Suc|), in the more perfect animals, is the 

 circuitous and guarded route, which every particle of nou- 

 rishment must take before it can be added to the general 

 mass of circuhiting fluid. 



By its admixture with the blood already contained in 

 these vessels, and its purification by the action of the air in 

 the respiratory organs (i?,) the chyle becomes assimilated, 

 and is distributed by the heart through appropriate'channels 

 of circulation called arteries (of which the common trunk, 



