In referring to the bony pelvis, Plate I, it will be observed that the same is in the nature of a canal, for the passage of the child into the world. At other times than during the child-bearing process, this canal must be effectually closed to perfectly retain its contents. To accomplish this purpose it is provided with a bottom or floor, which is to give this necessary support, not only to the organs that the pelvic cavity contains but also to the abdominal viscera that are superimposed upon them. In order to accomplish this, its outlet must be as effectually closed as the bottom of a box or barrel in which material things are stored for the purpose of carrying them from place to place. In the human subject this bottom is called the pelvic floor, because it serves the purpose of a bottom or floor to the pelvic canal.
The pelvic floor is not a simple structure but a complicated arrangement of organs and tissues. If we begin to examine it from below upwards, we first have its outer covering in the skin; then, the superficial and deep fascias, the triangular ligament of the bladder and a group of interlacing muscles. The organs that enter into the composition of the pelvic floor and interwoven with the preceding structures, are the bladder, the vaginal walls, the rectum and connective tissue. Examine Plate II.
Through this floor there are several openings, which are guarded by a special set of constrictor muscles that are termed sphincters. These are sufficiently strong in the bladder and rectum but in the vagina they would be entirely insufficient to close this canal effectually.
The vagina, or, for our purpose, it will be clearer if we say “vaginal canal,” divides the pelvic floor into an anterior and posterior segment, and it is by means of this division that the whole structure of the pelvic floor is weakened; this will be perceived at a moment’s reflection, when we compare it with the pelvic floor of the male, who has no vagina; and for this reason men are never troubled with the prolapses to which women are liable. Nature, however, has made an attempt to compensate this physical defect in a manner that reduces the weakness occasioned by the vaginal canal to its minimum. The vaginal canal does not enter the pelvic cavity in a directly upward or perpendicular course, but obliquely upwards and backwards, as may be seen by referring to Plate II. The result is that the intra-abdominal pressure falls on the vaginal walls from above, and thus compresses and approximates the anterior and posterior walls of the vagina to each other, so that it constitutes a self-closing valve, but, notwithstanding all these provisions, this slit or opening through the pelvic floor still remains the weakest point of the inclosure for the pelvic and abdominal viscera. When the causes are sought that underlie the various displacements of the uterus, they are generally to be found in an impairment of the pelvic floor, through some changes or accidents that are peculiar to pregnancy and delivery.
As we are also to inquire in the succeeding chapter into the displacements to which the womb is liable, it would greatly assist our understanding if we first got an idea of what constitutes the natural supports of the uterus? The word ligament is defined as anything that ties or unites one thing or part to another; a bandage; a bond. This is the idea in the popular mind, so that when the terms broad and round ligaments of the womb are employed it is supposed that they are for the same purpose for which ligaments are usually intended. This is, unfortunately for a clear understanding of the subject, a great mistake, because these ligaments are an exception to the generally accepted meaning of the term, for they neither tie nor support the uterus in its natural position. One may readily imagine that this erroneous conception would lead to a mistaken course in the treatment of most cases of displacements, because too much importance is bestowed upon structures that have no physiological bearing on the disease.
Drs. Hart and Barbour, of Edinburgh, in their “Manual of Gynecology,” which is the most scientific and practical work that has lately appeared in the English language, have this to say in speaking of the support of the uterus: “The question of the support of the uterus is still disputed. The broad and round ligaments have nothing to do with its support, they are only useful as giving fixed points for the contracting uterine muscles during parturition. The chief support is the compact unbroken pelvic floor, on which the uterus rests just as one sits on a chair. It is the whole pelvic floor that supports the uterus and viscera, not the perineum alone.” The perineum (see anatomical Plate II) is only a small though strong part of the pelvic floor. If the reader will now patiently review the organs that, together with the other tissues, constitute this floor, and this can be most profitably done by studying Plate II, there can be no confusion of ideas whatever. In the following pages I have occasion to refer to what is understood by the term pelvic floor.
CHAPTER XIX.
PROLAPSUS OR FALLING OF THE WOMB.