_Strassmann_ bases on clinical facts and on experiments the following view of the connection between ovulation and menstruation. The principal processes in the organism of the sexually mature woman run their course in a periodic rhythm resembling an undulatory movement, the acme of which occurs in the antemenstrual period with the aim of preparing for the development of an infantile organism. Whilst an ovum is maturing in the ovary, in the uterus, in dependence upon this maturation, the antemenstrual mucous membrane, fitted for the reception and nutrition of the fertilized ovum, is also undergoing development. At the acme of the undulatory movement, the graafian follicle ruptures and the ovum is liberated, to undergo fertilization in the infundibulum of the Fallopian tube. If fertilization fails to occur, or if for any reason the graafian follicle fails to rupture, then, in consequence of and at the time of the highest intra-ovarian tension, at the time, when the rupture of the follicle usually occurs, the extrusion of blood from the capillaries of the uterine mucous membrane begins. The intermediation between the ovary and the uterus is probably effected by means of the sympathetic ganglion in the ovary discovered by _Elizabeth Winterhalter_, and effected in this manner, that the stimulus proceeding from the ripening follicle passes along the nerve-fibrils surrounding the follicle to the processes of the nerve cells of this sympathetic ganglion, accumulating in these cells till a certain degree of intensity has been reached, and then, by means of other processes and of the vasomotor nerves, influencing the vessels of the uterus. _Gebhard_ likewise believes menstruation to be dependent on the ovarian function, and thinks that it is probably brought about in a reflex manner by the gradual growth of the ovarian follicles. It appears that most commonly at the time of menstruation a graafian follicle ripe to bursting is to be found in the ovary, but to this rule there are many exceptions. We cannot exclude the possibility, that the ovum from a follicle that burst after the commencement of the menstrual flow may be fertilized; but more commonly the ovum that is fertilized is that of the first period missed. The sudden decline in vital energy that occurs just before menstruation is explained by _Gebhard_ as a kind of atavism, dependent on the fact that many of the lower animals, butterflies, for instance, succumb as soon as they have fulfilled their duty of reproducing the species. A number of modern investigators, however, deny that any relation, temporal or causal, exists between ovulation and menstruation, and affirm that the latter process is quite independent of the former.