The body is divided into three separate stories by two partitions. The diaphragm, A, separates the cavity of the chest from that of the abdomen. The partition, D, forms a floor for the digestive cavity, F, and a roof for the pelvis; the pelvic cavity is occupied mainly by the generative organs. The upper part of the uterus is firmly fixed to the partition, D, by which the pelvis is covered. Now, the diaphragm, A, and the external respiratory muscles are in ceaseless motion performing the act of breathing. The diaphragm acts like the piston of a pump, both on the lungs above, and on the contents of the abdominal and pelvic cavities below. When it rises from B to A, it diminishes the size of the thoracic cavity, compresses the lungs, and assists in the expiratory part of breathing; at the same time it acts through the contents of the abdominal cavity on the pelvic roof, D, to which the uterus is attached, and raises it from D to C. When the diaphragm contracts, it descends from A to B, increases the size of the thoracic cavity, inflates the lungs, promotes the inspiratory part of breathing, pushes the walls of the chest and abdomen outward from F to E, and lowers the pelvic roof at the same time the uterus sinks from C to D. When the effect of these respiratory motions is not diminished by muscular debility, rigidity of the thoracic walls, or by unsuitable clothing, they have so direct an effect on the pelvic contents that the uterus and its appendages make two distinct motions every time a woman breathes.
When the diaphragm rises and the breath is expelled, the womb is elevated from one inch to one inch and a half, because the roof of the pelvis, to which it is attached, is lifted about this distance, because of gentle suction from above. The uterus and its appendages are thus kept in constant motion, up and down, chiefly by action of the muscles by which breathing is carried on.
Several influences combine to maintain the circulation of the blood. The pumping action of the heart and the affinity of the blood for the walls of the capillary vessels require to be assisted by the motion both of the body as a whole and of its parts in order to keep the circulation flowing equably through every tissue. Therefore muscular action and the resulting bodily motion play a very important part in maintaining the general and local blood circulation. During the contraction of a muscle, the blood current flowing through it is, for the time being, retarded, but when relaxation occurs the blood flows into its vessels more freely than if no momentary cessation had taken place. When the body or any of its parts is deprived of motion, the blood circulation stagnates, and the nutrition, general or local, as the case may be, promptly becomes impaired. This is specially true of the uterus. Gentle but constant motion is absolutely essential to keep up a healthy uterine blood circulation. Nature has provided for the automatic performance of all the ceaseless internal motions that are necessary to the continuance of life and the preservation of health; thus the heart beats, the respiratory muscles act, the stomach executes a churning motion during gastric digestion, the intestines pass on their contents by worm-like contractions, automatically without our supervision and without causing fatigue, being under the control of the sympathetic system of nerves chiefly.
It is equally true, but not so well recognized, that the previously described motions that are committed to the pelvic organs from the respiratory apparatus are absolutely necessary to the continued health of the uterus and its appendages. But the womb is not under the control of the voluntary muscles, therefore it cannot be directly moved by them, nor are its necessary motions influenced by the sympathetic system of nerves as are the heart, stomach, and intestines, etc., but it is fortunately under the indirect but positive control of involuntary muscles that never, as long as breathing continues, cease their work. Nature has thus made ample provision to keep the uterus in automatic motion. As before stated, the natural ceaseless heavings of the lungs, chest, and diaphragm, aided by the muscles inclosing the abdomen, have the duty assigned them of communicating automatic motion to the uterus and the other contents of the pelvis. When the diaphragm descends from A to B, and the lungs are filled with air, the uterus sinks in the pelvic cavity in obedience to the downward pressure from above, as before stated; the circulation through the uterus is then for a moment retarded, but the next instant, when the lungs are emptied of air and the diaphragm rises, the blood flows forward more freely than if it had not been momentarily obstructed.
Ample provision has thus been made to maintain a healthy circulation through the uterus.
The uterine motions I have described are fully adequate for the purposes indicated. But when the natural stimulus of motion is withheld, the circulation becomes sluggish causing congestion, which may develop into inflammation. Under these conditions the uterus gradually becomes displaced, falling backward, forward or downward as the case may be. The blood vessels by which the uterus is supplied thus have their caliber diminished by bending; the circulation through them is retarded just as the flow of water in a rubber tube is obstructed by a kink. A very good idea of what occurs in the uterus under the conditions just described may be obtained by winding a string around the fingers.
As the coats of the arteries are thick, and the pressure exerted by the ligature has less power to prevent the arterial blood flowing outward past the string to the end of the finger than it has to prevent the return of the venous blood toward the heart, therefore the part beyond the ligature soon becomes congested, the blood stagnating in the capillaries. If the ligature be sufficiently tight and kept on long enough, mortification will take place, but if the circulation be only moderately obstructed, the congestion will continue until ulceration occurs. A similar condition is developed in the uterus when the necessary natural stimulus of motion fails to be communicated to it or when it is so far out of its proper place that the circulation through it is obstructed.
I believe the above described condition to be a most potent but inadequately recognized cause of the various forms of uterine diseases that distress so many women.