That an extraordinary propensity to venery may be produced by introducing into the body a quantity of heat, admits now of a kind of demonstration from a fact mentioned by M. le Roy concerning phosphorus.[104] This substance is exceedingly apt to take fire on the application of a small degree of heat, and even by slight friction. It is now introduced into the materia medica, and is found to be a very powerful medicine, though dangerous on account of its inflammability, the heat and air contained in the human stomach being sometimes sufficient to set it on fire. The taking such a substance into the body therefore seems not much different from taking actual fire into it; and indeed M. le Roy mentions the case of a woman who had taken only a single grain, and who he says had been recovered, _by it_, from a putrid fever, but died suddenly from some imprudence. In this woman the whole substance of the body was found luminous upon dissection, and the hands of the operator continued luminous even after being washed. M. le Roy, having taken three grains of this fiery substance, found himself extremely incommoded by it for some hours, and was obliged to drink great quantities of very cold water. Next day he found his muscular powers amazingly increased, and had an _almost insupportable venereal irritation_. This we see was the consequence of throwing into the body a quantity of heat from without; but if the body itself emits that heat which it invisibly contains, the effects must be the same as though an extraneous quantity had been thrown into it. Neither are we to imagine that the _quantity_ of heat contained in our bodies is small or inconsiderable; for we have already seen that heat consists in the efflux from any substance, of an invisible and most subtile fluid, in all directions. When this flux is gentle, the heat is moderate, but in proportion to the activity of the discharge, the temperature becomes hotter and hotter, and if very violent, the cohesion of the parts is dissolved entirely, and the substance is said to be on fire. There is required therefore only some cause to begin the emission of this fluid; for as soon as this begins, the immense quantity with which we are surrounded, will supply more in abundance,[105] and continue so to do, as long as the original cause subsists, or until the substance can no longer bear the power which operates upon it. [104] Memoires de Societe Medicale, &c.