The Chyle, of which we have now traced the formation, is a fluid of uniform consistence, perfectly bland and unirritating in its properties, the elements of which have been brought into that precise state of chemical composition which renders them fit to be distributed to every part of the system for the purposes of nourishment. In all the lower orders of animals it is transparent; but the chyle of mammalia often contains a multitude of globules, which give it a white colour, like milk. Its chemical composition appears to be very analogous to that of the blood into which it is afterwards converted. From some experiments made by my late much valued friend Dr. Marcet, it appears that the chyle of dogs, fed on animal food alone, is always milky, whereas in the same animals, when they are limited to a vegetable diet, it is nearly transparent and colourless.

The chyle is absorbed from the inner surface of the intestines by the Lacteals, which commence by very minute orifices, in incalculable numbers, and unite successively into larger and larger vessels, till they form trunks of considerable size. They pass between the folds of a very fine and delicate membrane, called the mesentery, which connects the intestines to the spine, and which appears to be interposed in order to allow them that degree of freedom of motion, which is so necessary to the proper performance of their functions.