Hippocrates, older than Chiron the Centaur. Nature taught it to the first mother when she saw her first-born child putting some ugly pebble or lurid berry into its mouth. I know not in what language it was spoken, but I know that in English it would sound thus: Spit it out! Art can do something more than say this. It can sometimes reach the pebble or berry after it has been swallowed. But the great thing is to keep these things out of children's mouths, and as soon as they are beyond our reach, to be reasonable and patient with Nature, who means well, but does not like to hurry, and who took nine calendar months, more or less, to every mother's son among us, before she thought he was fit to be shown to the public. Suffer me now to lay down a few propositions, whether old or new it matters little, not for your immediate acceptance, nor yet for your hasty rejection, but for your calm consideration. But first, there are a number of terms which we are in the habit of using in a vague though not unintelligible way, and which it is as well now to define. These terms are the tools with which we are to work, and the first thing is to sharpen them. It is nothing to us that they have been sharpened a thousand times before; they always get dull in the using, and every new workman has a right to carry them to the grindstone and sharpen them to suit himself. Nature, in medical language, as opposed to Art, means trust in the reactions of the living system against ordinary normal impressions. Art, in the same language, as opposed to Nature, means an intentional resort to extraordinary abnormal impressions for the relief of disease. The reaction of the living system is the essence of both. Food is nothing, if there is no digestive act to respond to it. We cannot raise a blister on a dead man, or hope that a carminative forced between his lips will produce its ordinary happy effect. Disease, dis-ease,--disturbed quiet, uncomfortableness,--means imperfect or abnormal reaction of the living system, and its more or less permanent results. Food, in its largest sense, is whatever helps to build up the normal structures, or to maintain their natural actions. Medicine, in distinction from food, is every unnatural or noxious agent applied for the relief of disease. Physic means properly the Natural art, and Physician is only the Greek synonyme of Naturalist. With these few explanations I proceed to unfold the propositions I have mentioned.