LETTERS. 605
by the further diligence of Pecquet, who discovered the recep- tacle or reservoir of the chyle, and traced the canals thence to the subclavian veins, I shall tell you freely, since you ask me what I think of them. I had already, in the course of my dissections, I venture to say even before Aselli had published his book, 1 observed these white canals, and plenty of milk in various parts of the body, especially in the glands of younger animals, as in the mesentery, where glands abound; and thence I thought came the pleasant taste of the thymus in the calf and lamb, which, as you know, is called the sweetbread in our vernacular tongue. But for various reasons, and led by several experiments, I could never be brought to believe that that milky fluid was chyle conducted hither from the intestines, and dis- tributed to all parts of the body for their nourishment ; but that it was rather met with occasionally and by accident, and pro- ceeded from too ample a supply of nourishment and a peculiar vigour of concoction ; in virtue of the same law of nature, in short, as that by which fat, marrow, semen, hair, &c., are pro- duced ; even as in the due digestion of ulcers pus is formed, which the nearer it approaches to the consistency of milk, viz. as it is whiter, smoother, and more homogeneous, is held more laudable, so that some of the ancients thought pus and milk were of the same nature, or nearly allied. Wherefore, although there can be no question of the existence of the vessels them- selves, still I can by no means agree with Aselli in considering them as chyliferous vessels, and this especially for the reasons about to be given, which lead me to a different conclusion. For the fluid contained in the lacteal veins appears to me to be pure milk, such as is found in the lacteal veins [the milk ducts] of the mammae. Now it does not seem to me very probable (any more than it does to Auzotius in his letter to Pecquet) that the milk is chyle, and thus that the whole body is nou- rished by means of milk. The reasons which lead to a contrary conclusion, viz. that it is chyle, are not of such force as to compel my assent. I should first desire to have it demon- strated to me by the clearest reasonings, and the guarantee of experiments, that the fluid contained in these vessels was chyle, which, brought hither from the intestines, supplies nourish-
1 Published at Milan in 1622. ED.
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