UTERUS.
The uterus is that segnient of the genera tive track which lies between the lower ex tremities of the Fallopian tabes and the fornix or upper end of the vagina. In man it is normally formed by the complete coalescence of the two utenne cornua, which in most of the mammalia remain more or less distinct constituting the bicorned or divided uterus. These, in man and the quadrurnana, unite to form a. single symmetrical organ, serving for the passage of the seminal fluid, and for the reception, protection, nutrition, and final ex pulsion of the mature ovum.
The uterus is not altogether peculiar to the female. Like the mammary gland, it has its representative in the male, though only in a rudimental state. The existence of such a rudimentary organ is more easily shown in the male of many mammalian animals than in man, in whom, perhaps, it is the least conspicuous, and where its presence, as a type of structure, can only be proved by a close study of homologies, and by the aid of those occasional exemplifications of the true rela tions of this part which the comparatively rare occurrence of hermaphrodite forms affords.
Situation and position.— The unimpregnated uterus is situated entirely within the pelvis, where it lies deep among the other pelvic con tents, with many of which it is in immediate relation ; the bladder lying anteriorly, the rectum posteriorly, the ovaries and Fallopian tubes laterally, the small intestines supe riorly, and the vagina and perineum inferiorly with regard to it. These several parts, aided by the broad and round ligaments, serve to support the uterus and maintain it in its natu ral position. But this position will of neces sity vary according to the condition of the neighbouring organs, and in some degree also with the varying postures of the body.
The nature and degree of the variations in regard to situation and position of which the uterus is susceptible will be more easily understood after the ligaments and other con nections by which these movements are re strained have been described. At present it
will be only necessary to observe that the mo tions of the uterus are restricted chiefly to three directions. First, the broad ligaments, which maintain the organ nearly in the median line, permit by their laxity a slight deviation towards either side. Secondly, a certain amount of ascent and descent is allowed by the structures which attach the uterus to the lower part of the pelvis. But the former of these movements will be limited by the utero sacral ligaments, and the weight or pressure of the superincumbent viscera ; and the latter also especially by the same ligaments, and to a certain extent by the support derived from the posterior wall of the vagina and the parts which close the pelvis below. Thirdly, the uterus enjoys a certain range of motion in the direction of a line dravrn from pubes to sacrum in order to accommodate it to the state of fulness or emptiness of the adjacent viscera. For when the bladder is full and the rectum empty, the uterus will be carried nearer to the sacrum ; and conversely, with an empty blad der and a distended rectum, the position of the uterus will be proportionately nearer to the pubes ; and these alterations of position will be constantly and daily repeated.
But an equal degree of rnobility does not belong to every part of the uterus ; for while the movement of the cervix is limited by the attachment of the vagina and utero-sacral ligaments, the fundus is left entirely free to follow the alternate fillings and emptyings of the bladder. Thus a movement of nutation will result, the fundus uteri approaching the pubes and sacrum alternately ; and this is probably the greatest range of motion of which any portion of the uterus is normally suscep tible.
But allowing for these variations, there will still be an average position which the uterus occupies in the pelvis, and this may be as sumed to occur at the time when the bladder and rectum are both moderately distended.