Menstruation is the monthly discharge of a red fluid, common to females from fifteen or sixteen years of age to between forty and fifty; and it is held that, while a female menstruates, she is apt, and capable also, to conceive. Menstruation is a device of nature to relieve the system, or to preserve the balance of the circulation, from the non-fulfilment of her intentions, by the absence of procreation. It usually continues for four, five, or six days, and seldom exceeds a few ounces. Its suppression is usually attended with marked ill health, and many of the formidable complaints of females are attributable to its irregularities. When anticipated, the female encounters feelings of depression and lassitude, and exhibits an aspect of feeble health. As a physiological fact, women, before and after menstruation, are more desirous of the exercise of sexual privileges, and usually the approach of the menstrual flow is accompanied by a sexual orgasm. It has ever been deemed, by almost universal consent, prudent for married persons and others to abstain from the sexual embrace during that period. If only on the score of cleanliness, it should be observed; besides, the likelihood of establishing irritability, and the probability of interfering with this healthful provision of nature, should deter from the indulgence. In some countries, menstruating women are excluded from associating with the other sex altogether, and are even forbid mingling with household duties. At the close of this article will be found a series of prescriptions and suggestions for the removal of the various disturbances this function is liable to. The act of connexion is urged by what is called the sexual propensity. It is accompanied by feelings of the intensest kind: the acme of enjoyment is at the moment of seminal ejaculation. The penis is excited to erection by the influx or rush of blood into its cavernous or cellular structure; the scrotum becomes constricted, and compresses the testicles; the _vesiculæ seminales_, and the prostate gland, are also elevated by the muscles called _levatores ani_, as shown in the preliminary anatomical drawings, whence their use may now be better understood, as well as those of the perineal muscles, which all more or less assist in causing the prompt and forcible ejaculation of the spermatic fluid. “In[7] the female, the sense of enjoyment, _sub coitu_, appears to be principally excited by the friction of the _labia interna_ and _clitoris_, which are alike in a state of turgescence or erection. This nervous excitement, as in the male, often reaches such a degree of intensity that a kind of syncoptic state is induced.” A sense of contented lassitude follows, and the mind is permitted to return from the regions of excited imagination to its ordinary quietude.