To convince myself of this decomposing action of cream of tartar on calomel, I placed about a drachm of calomel in each of two small beaker glasses. In the one I put pure distilled water, in the other I added to the water about a drachm of cream of tartar. Heating them to about blood heat and allowing them to stand for a few hours, I filtered both liquids from the undissolved calomel. Ammonium sulphide, added to the filtered fluids, threw down from that which contained the cream of tartar a sensible amount of dark mercurial sulphide, while that which contained pure water gave no notable reaction. Evidently the cream of tartar had caused the decomposition of some of the insoluble calomel and had produced a soluble mercurial compound. All soluble compounds of mercury are active poisons in small doses, while, as was fully proven by Doctor Cooke's extraordinary practice with this substance, pure unchanged calomel is one of the most insoluble substances. Consequently it sometimes proved harmless in very large doses, as was the case when the copious watery discharges of cholera had removed most of the salts of the blood. The Doctor took no note of possible agencies which might make his master remedy occasionally poisonous, and scouted the careful practice of some of the older physicians in causing their patients to abstain from the use of common salt while taking calomel, a recommendation based upon valid experience, no doubt, which science has verified. The Doctor rose to two ounces, or tablespoonful doses, during the prevalence of Asiatic cholera in Lexington, but he did not confine this treatment to that fearful disease. The present writer has preserved one of the last of his mammoth doses--one of a dozen of the same weight (about an ounce)--which he prescribed for a medical student of the session of 1836-37, the subject of pneumonia, and who took eleven such doses in regular succession before he died. In Doctor Cooke's earlier practice, and in the treatment of less severe cases, he relied greatly on his famous pills--well known in the region of Lexington as "Cooke's Pills"--composed of equal parts of calomel, aloes, and rhubarb; or on tincture of aloes and the lancet, with the occasional use of a few other remedies. These constituted his sole armament with which to encounter disease. For he was a man of the strictest and most earnest honesty, sincerity, and zeal, and withal so wedded to his logical convictions that he would at any time have died a martyr to his well-matured beliefs. Indeed, according to the testimony of his friend, the late Lunsford P. Yandell, he seems thus to have been to some extent a martyr to his own theory and practice.