"In the first chapter it was stated that the _Ovæ_, or eggs, contained the rudiments or germs, from which, when impregnated by the male principle, new human beings were developed. These ovæ, however, are not prepared to undergo this development before the age of puberty, nor after the change of life, nor are the whole of them fit for conception even during the prolific period. It appears that they become fit for fecundation in succession, during the menstrual period, _one ovum,_ or more, _being ripened every month_! When fully perfected it separates from the ovary and is lost, unless conception occurs, in which case it passes along the fallopian tube into the Womb, and then develops into the fœtus. Here then we see the cause of the menses; the ripening of the ovum causes a local excitement, and congestion, in the ovary and womb, which increases till the period when it is thrown off, and then the accumulated fluid is discharged, the excitement subsides, and a new development commences. "This curious process is termed by some physiologists the monthly _ponte_, or _laying of eggs_, and by others the _Ovarian labor_, or _birth_! A small scar is left on the ovary at the point where the ovum separates, which fades away after a time, but a number of them may always be observed on the ovaries of those who have long menstruated. In those who die during menstruation the ovaries are found very red, and full of blood, and sometimes one of the ovæ will be found swelled, and just ready to burst through, or the ruptured opening may be seen through which it has actually escaped. "Precisely the same phenomenon occurs in the lower animals, excepting that their periods are more extended; some of them occurring annually, and others at still longer intervals. Some of the monkeys even have a species of real menstruation. "These important facts, by enabling us to understand what causes menstruation, give us an insight also into the nature of its derangements, and the conditions required for their regulation. When we call to mind also the close sympathy between the uterine organs and every other part of the system, it shows us how important a proper menstruation is to the general health, because without it those organs must be diseased, and consequently every other part of the system liable to suffer with them.