THE structures which we are about to describe will be found to have most important bearings upon the conceptions no* entertained of the physiology of the lymphatic system, as well as upon its anatomy; for none of the functions seriously attributed to it at the present day will be found capable of explaining its existence and relations in the wallsof the largerlymphatics, and the only function which, in our opinion, may hypothetically be held to account for its presence there, will also apply equally, in general, throughout the body, giving an additional importance to the lymphatic system.

The presence and peculiar position of the lymphatics within the walls of the larger lymphatics themselves appear, withour present conceptions of the physiology of the system, to" be nothing more nor less than an anatomical curiosity. Although the same thing cannot be said of the lymphatics of the walls of arteries and veins, and however great a dissimilarity may, at first sight, appear to exist in the relation of the lymphatics to the different structures which enter into the different coats or layers forming the walls of the three kinds of vessels, we shall be able to recognise with tolerable clearness that the plan of distribution is the same in all three. It is somewhat curious that, notwithstanding the fact that in former days the idea of the existence of lymphatics within vascular walls (and indeed everywhere) had its origin in this country as a hypothetical deduction from certain experiments on animals performed by the Hunters and VOL. XVII. A