Chemistry makes such rapid strides of late that it is impossible for the medical man in ordinary practice to keep pace with it. We have ptomaines and leucomaines, and in the literature of the journals these two terms are used indiscriminately, which is unfortunate, as tending to create confusion. While ptomaines are those alkaloidal products of metabolism belonging to the cadaver, or to any dead organism, whether animal or vegetable, the term is now applied to the same products in living tissues and which really are not ptomaines, but leucomaines. Chemically speaking, both ptomaines and leucomaines exist in the forms of monamines, diamines, and triamines, and have hitherto been regarded as resulting from the oxidation of ammonium salts by abstraction of water or from acids by substitution of amidogen. Yet the bacteriologists assure us that they are the secretions, or rather excretions, of bacteria, just in the same way that the strata of non-igneous rocks of the earth are formed primarily by the secretion, and secondarily by the excretion, of calcareous shells of diatoms, or of the cretaceous shells of those protozoans entitled rhizapods. Elsewhere in the SUMMARY I have expressed myself to this effect in nearly the same language, and while it may seem pedantic, it should be borne in mind that this is the age of terminology. We, each of us, have our special ties—shall I say hobbies? One of us making the eye a specially will make use of ophthalmological terms. Another turns his attention to the technology of animal tissues, and still another, with an eye towards the bacteriological existences, leads us into a labyrinth of Greek and Latin technics. We are talking of ptomaines and leucomaines, and that their existence is probably due to bacteria. These are regarded as toxines, and certain diseases are said to be caused by these toxines, and not from the bacteria themselves directly, but indirectly. I appreciate the idea that the curative results of these diseases are due to the antagonism of the remedies to these toxines, and not to the destruction of the bacteria. Before we inquire into the curative action of remedies we must first find out how these toxines produce disease. The tendency is to trace the origin of all disease to a change in the protoplasmic cells. This change is evidently due to a toxine. A healthy physiological change in the cells may be termed metabolism, while an unhealthy or pathological change may be termed katabolism. The question arises, in what way does katabolism arise from these toxines? It occurs to me that it must be due to chemical affinity, or as it is sometimes very properly called, _chemism_.