Third, the Tubal Theory.-- Lawson Tait thought that thorough removal of the tubes was far more essential in determining the menopause, and that cases of periodically recurring hemorrhage after the removal of the ovaries were to be explained by the fact that the tubes had not been sufficiently removed. As an anatomic and surgical fact, the tubes can never be wholly excised unless the upper part of the uterus is also amputated.
Fourth, the Nerve Theory of Menstruation.-- This is based upon the following views:
1. That menstruation is a process directly controlled by a nerve-center situated in the lumbar region of the spinal cord.
2. That the menstrual impulses reach the uterus through two sets of nerves.
3. That menstruation is the result of nerve irritation, vascular congestion, and the subsequent relief of these by hemorrhagic discharges.
4. That hemorrhage from the uterus is the result either of a local uterine condition, or of influences outside of the uterus acting directly on the center.
5. That the removal of the appendages arrests menstruation by preventing the propagation of uterine influences to the center.
Uterine Nerve Supply.-- One set of nerves causes contraction of the muscular fibers of the uterus, while the other set transmits impulses which bring about its vascular engorgement; and they are probably concerned in bringing about the determination of blood to the uterus and its appendages, which is so marked a feature of the menstrual process.
As the result of long-continued investigation, Johnstone has come to the conclusion that the lining membrane of the uterus belongs to that class of organs whose function it is to replace organic waste. "Menstruation is a periodic wasting away of those corpuscles that are too old to make a placenta." He has further found that, as compared with the uteri of very many of the lower animals, the human uterus is very scantily supplied with lymphatics, and the only way to rid the uterus of the overripe, and therefore consequently useless, tissue is to wash it out through the vagina by a blood-stream. The tough wall of the human uterus and the increased blood-pressure caused by the erect position cause the difference between menstruation in the human female and rut in the lower animals.