ECT. xxxvii. 3. DIGESTION; SECRETION, & c . 527 



teal or lymphatic vefiels, as foon as it is produced .; 

 which is not eafy to imitate in the laboratory. 



Thefc ladeal veffels have mouths, which are ir- 

 ritated into aflion by the ftimuliis of the fluid, 

 which fur rounds them ; and t>y animal feledion, 

 or appetency, they abforb fucli part of the fluid as 

 is agreeable to their palate ; thofe parts, for in- 

 ftance, wljich are already converted into chyle, be- 

 fore they have time to undergo another change by 

 a vinous or acetous fermentation. This animal ab- 

 forption of fluid is almoft vifible to the naked eye in 

 the a&ion of the pun6la lacrymalia ; which im- 

 bibe the tears from the eye, and difcharge them 

 again into ihe noftrils. 



III. The arteries conftitute another refervoir of a 

 changeful fluid; from which, after its recent oxy- 

 genation in the lungs, a further animal feleclion 

 of various fluids is abforbed by the numerous glands ; 

 thefe fek(S their refpe&ive fluids from the blood, 

 which is perpetually undergoing a chemical change ; 

 but the fele&ion by thefe glands, like that of the 

 ladleals, which open their mouths into the digefting 

 aliment in the ftomach, is from animal appetency, 

 not from chemical affinity ; fecretion cannot there- 

 fore be imitated in the laboratory, as it con lifts in 

 a fele&ion of part of a fluid during the cheiiiical 

 change of that fluid. 



The mouths of th la&eals, and lymphatics, and 

 the ultimate terminations of the glands, are finer 

 than can eafily be .conceived ; yet it is probable, 

 that the pores, jpr imerllices of ihe parts^ or coats^ 

 which conftitute thefe ultimate veffels, may ftill 

 have greater tenuity ; and that thefe pores from 

 the above analogy mu ft poffefs a fimilar power of 

 irritability, and abforb by their living energy the 

 particles of fluid adapted to their purpofes, whether 

 to replace the parts abraded or diffolved, or to 

 elongate and enlarge themfelves. Not only every 



kind 



