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accounted for, if we recollect, that at the time when these vessels, and the structure of this part, were discovered, the lymph, and every thing belonging to it, was utterly unknown; and that the vessels in question were first seen and considered as performing another and more remarkable office: which circumstance, it should seem, has prevented succeeding authors from being duly attentive to them in the capacity of lymphatics. However this be, it is certain, that the lymphatics of the mesentery, commonly called the lacteals, differ from those of the other parts in no one particular, save that occasionally they carry chyle instead of lymph; or rather carry lymph mixed, at stated times (that is, for two or three hours after the creature has taken food) with an emulsion of vegetable and animal substances, and coloured white by that mixture. At other times, (that is, during sixteen or eighteen hours out of the twenty-four) they contain nothing but lymph; and are, in every respect, mere lymphatic vessels, not to be distinguished from those in any other part of the body. Their structure is the same; the membrane of which they are formed, their valves, the lymph which they contain, the glands thro' which they pass, their direction from smaller tubes to larger, and from these to the blood, differ in nothing from what we observe of the other lymphatics. Their lymph, in the mean time, is without doubt or controversy supplied from the cavity of the intestines; being the watery moisture continually exhaled there for the purposes of digestion, and for the preservation of the alimentary canal, and as continually taken up by the roots or extremities of these vessels, in
