SECT. XXXVII. 3. i. SECRETION, &c. 36: 



chemical procefs, termed digeftion ; which, however, chemiftry 

 has not yet learnt to imitate out of the bodies of living animate 

 or vegetables. This procefs feems very fimiiar to the faccharine 

 procefs in the lobes of farinaceous feeds, as of barley, when it 

 begins to germinate ; except that, along v/ith the fugar, oil and 

 mucilage are aiio produced , which form the chyle of animals, 

 which is very fimilar to their milk. 



The reafon, I imagine, why this chyle-making, or faccharine 

 procefs, has not yet been imitated by chemical operations, is 

 owing to the materials being in fuch a fituation in refpedl to 

 warmth, moiilure, and motion ; that they will immediately 

 change into the vinous or acetous fermentation ; except the 

 new fugar be abforbed by the numerous lacleal or lymphatic 

 veflels, as foon as it is produced j which is not cafy to imitate 

 in the laboratory. 



Thefe lacteal vefTels have mouths, which are irritated into ac- 

 tion by the ftimulus of the fluid which furrounds them ; and by 

 animal fe!eHon, or appetency, they abforb fuch part of the flu- 

 id as is agreeable to their palate ; tho e parts, for inftance, 

 which are already converted into chyle, before they have time 

 to undergo another change by a vinous or acetous fermentation. 

 This animal abforption of fluid is almoft vifible to the naked eye 

 in the aftion of the pun: la lachrymalia ; which imbibe the tears 

 from the eye, and difcharge them again into the noftrils. 



III. The arteries coniiitute another refervoir of a changeful 

 fluid ; from which, after its recent oxygenation in the lungs, a 

 further animal feledlion of various fluids is abforbed by the nu- 

 merous glands , thefe felel their refpe&ive fluids from the 

 blood, which- is perpetually undergoing a chemical change ; but 

 the feledlion by thefe glands, like that of the lacleals, which 

 open their mouths into the digefling aliment in the ftomach, is 

 from animal appetency, not from chemical affinity ; fecretion 

 cannot therefore be imitated in the laboratory, as it confifts in a 

 fele&ion of part of a fluid during the chemical change of that 

 fluid. 



The mouths of the lafteals, and lymphatics, and the ultimate 

 terminations of the glands, are finer than can eafily be conceived ; 

 yet it is probable, that the pores, or interfaces of the parts, or 

 coats, which conftitute thefe ultimate veflels, may ftill have 

 greater tenuity ; and that thefe pores from the above analogy 

 mull poflefs 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 diflblved, or to elongate 

 and enlarge themfelves, Not only every kind of gland is thus 

 endued with its peculiar appetency, and feledts the material 

 VOL. I. Y Y agreeable 



