Recent experimental investigations on this subject have shown that the interconnection between the female genital organs and the organism as a whole, between the functions of the reproductive organs and the functions of other organs, does not depend on nervous influences only, but that in this interconnection the blood vascular system and the lymphatic vascular system also play their parts. _Goltz_ has proved by actual experiment that the nervous influence on menstruation and ovulation is not the only determinant. In a bitch, he divided the spinal cord at the level of the first lumbar vertebra, and observed, as soon as the animal had recovered from the operation, the appearance of the usual signs of heat; the bitch was impregnated, and gave birth to one living and two dead puppies; lactation and sucking took place as in a normal animal. When the bitch was killed and the body examined it was found that no reunion had taken place in the severed spinal cord. The experiments of _Halban_ gave similar results. He found that in apes, if the ovaries are removed from their normal situation and successfully transplanted to some region remote from the genital organs, the animals remain capable of menstruating. But if the ovaries, which have been transplanted beneath the skin or beneath the peritoneum, are subsequently entirely removed, menstruation, which has continued regularly after the first operation, ceases altogether after the second. It follows from these experiments that the cessation of the menstrual process may be considered to be brought about through the intermediation of the lymphatic or blood-vascular system, by the absence of a kind of internal secretion. _Loewy_ and _Richter_ have further proved by experiment that in spayed bitches the consumption of nitrogen is less by about 20 per cent. and the entire gaseous interchange less by about 9 per cent., as compared with what takes place in normal animals, and that this change in respiratory metabolism lasts for a long time after the oöphorectomy, for as much as nine to twelve months. If dried ovaries are given to such animals in their food, the gaseous interchange rises to the former level and even higher. The undulatory movement of the vital processes in woman is apparently in some way dependent on ovulation, though the nature of the connection has not hitherto been fully elucidated. This view is confirmed by the fact that no such rhythmic variation in the bodily functions can be detected either in girls under thirteen years of age, or in women from fifty-eight to eighty years of age in whom menstrual activity has entirely disappeared. The menstrual rhythm begins at puberty and ends when ovulation ceases.