If conception occurs, of course, all doubt is removed. If the sex cannot be definitely determined by such examination, it is best to consider the case one of male pseudo-hermaphroditism, which is the usual form, and to treat the individual as a male. CHAPTER XXXIV. DISORDERS OF MENSTRUATION. Menstruation, or the regular periodical discharge of blood from the uterus, is a phenomenon that occurs only in the human race and in some monkeys. The anatomical changes that accompany menstruation have not yet been definitely determined. In some species of monkey--_Semnopithecus entellus_ and _Macacus rhesus_[2]--the following changes appear to take place at the menstrual periods: The endometrium first becomes swollen and congested as a result of the growth of the stroma, and increase in the number and size of the blood-vessels. The vessels in the superficial part of the stroma degenerate and break down, and blood is extravasated into the meshes of the stroma network. The extravasated blood collects into lacunæ which lie close beneath the uterine epithelium. Finally the lacunæ rupture and the blood escapes into the cavity of the uterus, forming the menstrual clot. Then a fresh epithelium grows over the torn surfaces, new blood-vessels are formed, the stroma shrinks, and the endometrium of the intermenstrual period is restored. Nothing is known with any degree of certainty regarding the cause and significance of menstruation. There is much diversity of opinion in regard to the coincidence of ovulation and menstruation. Heape has shown that for monkeys ovulation and menstruation are not necessarily coincident; in forty-two menstruating specimens of _S. entellus_ not one had a recently discharged follicle in either ovary. In monkeys, therefore, menstruation may take place without ovulation, and it is probable that the same is true for the human female. Ovulation and conception may occur in the human female when menstruation is absent; pregnancy not infrequently occurs during the amenorrhea associated with lactation, and in India, where the girls are married at a very young age, pregnancy and child-birth occur before menstruation has begun. Leopold (quoted by Hirst) in an examination of twenty-nine pairs of ovaries removed on successive days up to the thirty-fifth after a menstrual period, found a Graafian follicle bursting on the eighth, twelfth, fifteenth, sixteenth, eighteenth, twentieth, and thirty-fifth days after the menstrual period. Thus ovulation frequently occurred without menstruation during the intermenstrual interval. In five cases there was no ovulation at the menstrual period, or menstruation occurred without ovulation. It seems probable, therefore, that the ripening of the ovum in the ovary is independent of the process of menstruation, though the increased blood-supply to the generative organs during menstruation may, to a certain extent, determine the time of ovulation when a sufficiently ripe ovum is present.