Other observations, well examined, afford a sixth cause, which may, at the first superficial view, appear of the slightest, but which no intelligent naturalist will readily pronounce null. All living bodies perspire. Every instant there exhales through, perhaps, one half of the pores of our skin, a humor of extreme tenuity, and which is a great deal more considerable than all our other evacuations: at the same time, another kind of pores admit a part of the fluids which surround us, and convey them into the vessels. These are _the invisible torrents_ (to use M. SENAC’s happy expression) that have their egress and regress into our body[91]. It stands demonstrated, that, in some cases, this insorption is enormous. The strong and healthy perspire the most: the weak, who have hardly any atmosphere of their own, inhale more. Now the miasms, or perspired matter of healthy persons, contains something nutritious and corroborative, which inhaled by another, contributes to give him vigor. These are observations, which explain why the _young virgin_, selected to cherish DAVID, by lying in his bosom, gave him strength; why the same experiment has succeeded with other old men, to whom it had been prescribed; why that process weakens the young person, who loses, without receiving anything; or rather receives, in return, faint, sickly, corrupt, putrid exhalations, which cannot but be noxious. Now, in the time of coition, people perspire more than at any other, the force of the circulation being augmented. This perspiration is also, probably, more active, more spirituous, than at any other time: it is a real loss that is, on that occasion, sustained, and which takes place, in whatever manner the emission of the seed is made, as it depends on the agitation that accompanies it. In coition it is reciprocal, and then, the one inhales what the other perspires. This exchange stands unquestionably proved by sure observations. I saw myself, not long ago, one, who having no gonorrhœa, no cutaneous symptom of the _lues_, had given the venereal distemper to a woman, who, at that instant was giving him the itch in exchange. In coition, then, there is a sort of mutual compensation of loss on both sides. But in the case of self-pollution, the person guilty of it loses, and in lieu of his loss, receives nothing. An observation of the effect of the passions discovers a seventh cause of evil, in the difference between those who indulge themselves with women, and the self-pollutors; a difference which is intirely to the disadvantage of these last.