Sect. XXIII. 6. SYSTEM. a 1 1 



as the lacleals and lymphatics are a fyfteni of veiTels abforbing 

 chyle and lymph. See Sect. XXVII. i . 



VI. The movements of their adapted fluids in the various 

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

 veiTels in ccnfequence of two kinds of ftimulus, one of which may 

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

 {el to feize, and, as it were, to f wallow the particles thus felecl> 

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

 glands, veins, and other abibr bents, which may be called glandu- 

 lar appetency. The other kind of ftimulus may be compared 

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

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

 the arteries ; the fame again ftimulates the arteries to contract, 

 ai;d carry forwards the blood to their extremities, the glands 

 and capillaries. Thus the mefenteric veins abforb the blood 

 from the interlines by glandular appetency, and carry it for- 

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

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

 extremities, the various glands, which conftitute the liver. 



It feems probable, that at the beginning of the formation of 

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

 ity felt by the glands during fecretion, as is now felt in the a£fc 

 of f wallowing palatable food ; and that a difagreeable fenfation 

 •was originally felt by the heart from the diftention 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 fyftem, except when the veflels are 

 ^ifeafed by inflammation. 



SECfc 



