SECT. XXIIL "<5. SYSTEM. 2 1 1 



as the lafteals and lymphatics are a fyftem of veflels abforbing 

 chyle and Jymph. See Sea. XXVII. i. 



VI. The movements of their adapted fluids in the various 

 veflels of the body are carried forwards by the actions of thofe 

 veflels in confequence of two kinds of flimulus, one of which may 

 be compared to a pleafurable fenfation or defire inducing the vef- 

 fel to ieize, and, as it were, to fwallow the particles thus felecT:- 

 ed from the blood ; as is done by the mouths of the various 

 glands, veins, and other abforbents, which may be called glandu- 

 lar appetency. The other kind of ftimulus may be compared 

 to disagreeable fenfation, or averfion, as when the heart has re- 

 ceived the blood, and is ftimulated by it to pufh it forwards into 

 the arteries j the fame again ftimulates the arteries to contraft, 

 and carry forwards the bloo.d to their extremities, the glands 

 and capillaries. Thus the mefenteric veins abforb the blood 

 from the inteftines by glandular appentency and carry it for- 

 ward to the vena portarum ; which acting as an artery con- 

 tracts itfelf by difagreeable ftimulus, and pufhes it to its ramified 

 extremities, the various glands, which conftitute the liver. 



It feems probable thar at the begining of the formation of 

 thefc veflels in the embryon, an agreeable fenfation was in real- 

 ity felt by the glanJs during fecretion, as is now felt in the act 

 of fwallowing palatable food ; and that a difagreeable fenfation 

 was originally felt by the heart from the detention occafioned 

 by the blood, or by its chemical ftimulus ; but that by habit 

 thefe are all become irritative motions ; that is, fuch motions 

 as do not affect the whole fyitem, except when the veflels are 

 difeafed by inflammation. 



SECT 



