In cases of sterility, different means have been employed to discover whether the defect was to be imputed to the man or the woman. Of these, inspection is the chief; and indeed, if the sterility be occasioned by an external fault in the conformation, this is sufficient. But if the defect is in the internal organs, it is almost impossible to discover or remove it. There are men, to all appearance well formed, who want the genuine sign of a proper conformation; and others who have it in so slight a degree as to make the mark of virility extremely equivocal. This is the most animal part of the human frame, and is constantly under the influence of instinct, and not governed by that of the mind. Many young persons of the purest ideas have been subjected to the liveliest sensations, though ignorant of pleasure, or the cause, and others remain cold and languid notwithstanding the efforts of imagination. When sterility does not arise from any defect in external conformation, it more frequently proceeds from the women than the men; for, besides the injurious effects of the fluor albus, I conceive there is another material cause. In the course of my experiments, as related in the preceding volume, I observed there were small protuberances in the female testicles which I called glandular bodies; they originate under the membrane of the testicle, in a short time begin to swell, and then opening, a fluid issues therefrom; from this time they begin to decay, and having disappeared, they are immediately succeeded by others, from which the testicles are constantly undergoing a kind of alteration; and I am inclined to think, that if any circumstance takes place to interrupt the necessary exercise of the vessels, the seminal liquor will become corrupt, and sterility also will follow. Sometimes conception precedes puberty. Numbers of women have become mothers before the smallest appearance of the menstrua: and some to whom this evacuation was never known have brought forth children. Instances of this occur in our own climate, without travelling for them to Brazil; where whole nations, we are told, are perpetuated without any woman being subject to the menstrual discharge; an evident proof, that it is not the substance of this discharge, but the seminal liquid of male and female which are essentially necessary to generation. It is also known that the cessation of the menses, which generally happens about the age of forty or fifty, does not always disqualify women from conceiving, and that some women have really become pregnant at the age of sixty or seventy. These examples, however frequent, may be considered as exceptions to the general rule; but they are sufficient to convince us that the menstrual blood is by no means the constituent principle of generation.