Letters 



In some they proceed to the liver, in others to the 

 porta only, and in others still to neither of these. In 

 some creatures they are seen to be extremely numerous 

 in the pancreas ; in others the thymus is crowded with 

 them ; in a third class, again, nothing can be seen of 

 them in either of these organs. In some animals, 

 indeed, such chyliferous canals are nowhere to be dis- 

 covered (vide Liceti Epist. xiii, tit. ii, p. 83, et Sen- 

 nerti Praxeos, lib. v, tit. 2, par. 3, cap. i); neither do 

 they exist in any at all times. But the vessels which 

 serve for nutrition must necessarily both exist in all 

 animals, and present themselves at all times ; inasmuch 

 as the waste incurred by the ceaseless efflux of the 

 spirits, and the wear and tear of the parts of the body, 

 can only be supplied by as ceaseless a restoration or 

 nutrition. And then, their very slender calibre seems 

 to render them not less inadequate to this duty than 

 their structure seems to unfit them for its performance : 

 the smaller channels ought plainly to end in larger 

 ones, these in their turn in channels larger still, and the 

 whole to concentrate in one great trunk, which should 

 correspond in its dimensions to the aggregate capacity 

 of all the branches ; just such an arrangement as may 

 be seen to exist in the vena portse and its tributaries, 

 and farther in the trunk of the tree, which is equal 

 to its roots. Wherefore, if the efferent canals of a fluid 

 must be equal in dimensions to the afferent canals 

 of the same fluid, the chyliferous ducts which Pecquet 

 discovers in the thorax ought at least to equal the two 

 ureters in dimensions ; otherwise they who drink a 

 gallon or more of one of the acidulous waters could not 

 pass off all this fluid in so short a space of time by 

 these vessels into the bladder. And truly, when we 

 see the matter of the urine passing thus copiously 

 through the appropriate channels, I do not see how 

 these veins could preserve their milky colour, and the 

 urine all the while remain without a tinge of whiteness. 

 I add, too, that the chyle is neither in all animals, 



