An impersonal and scientific knowledge of the structure of our bodies is the surest safeguard against prurient curiosity and lascivious gloating. This knowledge at the back of the minds of the lovers, though not perhaps remembered as such, may also spare the unintentioned cruelty of behaviour which so readily injures one whose lover is ignorant. What actually happens in an act of union should be known. After the preliminaries have mutually roused the pair, the stimulated penis, enlarged and stiffened, is pressed into the woman's vagina. Ordinarily when a woman is not stimulated, the entrance to this canal, as well as the exterior lips of soft tissue surrounding it, are dry and rather crinkled, and the vaginal opening is smaller than the man's distended penis. But when the woman is what is physiologically called tumescent (that is, when she is ready for union and has been profoundly stirred) local parts are flushed by the internal blood supply and to some extent are turgid like those of the man, while a secretion of mucus lubricates the opening of the vagina. In an ardent woman the vaginal orifice may even spontaneously contract and relax. (So powerful is the influence of thought upon our bodily structure, that in some people all these physical results may be brought about by the thought of the loved one, by the enjoyment of tender words and kisses, and the beautiful subtleties of wooing.) It can therefore be readily imagined that when the man tries to enter a woman whom he has _not_ wooed to the point of stimulating her natural physical reactions of preparation, he is endeavouring to force his entry through a dry-walled opening too small for it. He may thus cause the woman actual pain, apart from the mental revolt and loathing she is likely to feel for a man who so regardlessly uses her. On the other hand, in the tumescent woman the opening, already naturally prepared, is lubricated by mucus, and all the nerves and muscles are ready to react and easily accept the man's entering organ. This account is of the meeting of two who have been already married. The first union of a virgin girl differs, of course, from all others, for on that occasion the hymen is broken. One would think that every girl who was about to be married would be told of this necessary rupturing of the membrane and the temporary pain it would cause her; but even still large numbers of girls are allowed to marry in complete and cruel ignorance.