48 THEPHILOSOPHY 



The inftruments and procefs of digeftlon fall next to be confider* 

 ed. The ftomach is a membranous and mufcular bag furniftied with 

 two orifices : By the one it has a communication with the oefopha- 

 gus, or gullet, and by the other with the bowels, which begin at the 

 ftomach and terminate at the anus. In the ftomach and inteftines 

 there are immenfe numbers of minute veflels called laSieals, the 

 mouths of which arc conftantly open for the reception of the nutri- 

 tious particles. After being moiftened and lubricated by the faliva, 

 the food is received into the ftomach, where it is ftill farther diluted 

 by the gaftric juice, which has the power of diflblving every kind 

 of animal and vegetable fubftance. When the food has remained 

 fome time in the ftomach, it is reduced to a grayith pulp, mixed 

 with fome chylous or milky particles. The thinner and more per- 

 fedly digefted parts of the food gradually pafs through the pylorus, 

 or lower aperture of the ftomach, into the inteftines, where they are 

 ftill farther attenuated and digefted by the bile and pancreatic juices. 

 While the food is in this fluid ftate, it receives the denomination of 

 chyle, and Is continually abforbed by the mouths of the lafteal veins. 

 Thefe veftels arife, like net-work, from the inner furface of the In- 

 teftines, pafs obliquely through their coats, and, running along the 

 mefentery, unite, as they advance, Into larger branches, and at laft 

 terminate in the thoracic dufl, or general receptacle of the chyle. 

 Befide the lafteals, there is another fyftem of vefl"els called lympha- 

 tic, or abforbent veins : They are minute pellucid tubes, and gene- 

 rally He clofe to the large blood-veflels. The lymphatics from all 

 the lower parts of the body gradually unite as they approach the 

 thoracic duft. Into which they pour a colourlefs fluid by three or 

 four large trunks ; and the lymphatics from all the fuperlor parts 

 of the body Hkewlfe difcharge their lymph Into the fame dud as It 

 runs upward to terminate In the left fubclavlan vein. By this cu- 

 rious and beautiful machinery, the chyle and lymph, which confift 

 01 the nutritious matters extracted from the food, enter the circu- 



I latlng 



