In all due respect to him I quote it from the sketch of that remarkable man, as given in the _Popular Science Monthly_, as specially bearing on my discovery: "Mayer observed while living in Java, that the _venous blood_ of some of his patients had a singularly bright red color. The observation riveted his attention; he reasoned upon it, and came to the conclusion that the brightness of the color was due to the fact that a less amount of oxidation was sufficient to keep up the temperature of the body in a hot climate than a cold one. The darkness of the venous blood he regarded as the visible sign of the energy of the oxidation." My observation leads me to the contrary, that the higher the temperature the more rapid the breathing to get clear of the excess of carbon, and hence more oxygenation of the blood which will arterialize the venous blood, unless there is a large amount of carbonized matter from the tissues to be taken up. Nor must it be denied because of the reasoning as presented to my mind by some outside influence in my soliloquy when I first exclaimed, "Nature's anaesthetic," where the argument as to the effects of nitrous oxide gas being due to an excess of oxygen was urged, and that common air breathed in excess would do the same thing. I am not sure that _it_ was correct, for the effects of nitrous oxide is, perhaps, due to a deprivation of mechanically mixed air. Knowing what I do of theory and practice, I can say with assurance that there is not a medical practitioner who would long ponder in any urgent case as to the thousand and one theories of the action of remedies; but would resort to the _practical_ experience of others and his own finally. (What surgeon ever stops to ask how narcotics effect their influence?) After nearly thirty years of association with ether and chloroform, who can positively answer as to their _modus operandi?_ It is thus with nearly the whole domain of medicine. It is not yet, by far, among the sciences, with immutable laws, such as we have in chemistry. Experimentation is giving us more specific knowledge, and "practice alone has tended to make perfect." (Then, gentlemen will not set at naught my assertion and practical results. When I have stated my case in full it is for _you_ to disprove both the theory and practice annunciated. So far as I am concerned I am responsible for both.) You will please bear with me for a few minutes in my attempt at theory.