Regarding this explanation, which had been given by many preceding authors (see Mauriceau, tom. i. p. 97.; Smellie, vol. i. p. 183. et seq.), but which Gooch was, I believe, the first to illustrate by dia grams, it appears to me that much imagination has been exercised. The illustrations usually given are evidently diagrams supplied for the purpose of aiding the description of the process, as it has been supposed to occur, from examination of the part by the finger during life, but they give a very imperfect notion of the actual state of the cervix in pregnancy, as ascertained by dissection.
by the variable condition of the internal os uteri, or upper orifice of the cervix. If this remains unyielding until the time of labour, then the finger, on being placed within .the cervix, traverses the whole length of the canal before it reaches any part of the child ; and the general form and substance of the cervix being retained, the neck is said to be unob literated. Such is usually the state of parts after repeated pregnancies. But if the in ternal or upper os yields readily, as it usually does in the more advanced stag,e of a first pregnancy-, then the head of the child gradu ally settles down upon the lower orifice, press ing aside the soft and yielding wall of the cervix, which thus forms for it a shallow, cup like, or funnel-shaped recess, that may be so far said to be added to the uterine cavity ; and the finger, on passing within the os readily, touches the child, without having to traverse any length of cervix.
'When, therefore, the term, shortening of the uterine neck, is employed, it should be understood to imply that change which takes place from the hypertrophy and lateral exten sion of the vaginal portion of the cervix, com bined sometimes with a separation of' the cer vical walls from each other, occasioned by the descent of the head of the child ; the degree of this descent being regulated by the amount of yielding of the internal os uteri. But it does not signify any alteration in the anato mical condition of the cetyix and body of the uterus, which in every case retain their dis tinctive characteristics to the end of preg nancy : while the dilatation of the cervical canal is only an occasional occurrence, limited to the last stage of pregnancy, and having nothing to do vvith that apparent shortening which begins after the fifth month.
Position actual and relative. — The enlarge ment which the uttrus undergoes during ges. tation, occasions of necessity very considerable alterations in its actual and relative position. On the occurrence of pregnancy, the organ, at first concealed within the pelvis, sinks, by its increased weight, lower than usual within that, cavity; and, pressing upon the bladder and rectum, occasions sotnetimes an irritable con dition of these parts. But usually at the end of the third month, the fundus may be felt emerging from the pelvic cavity ; and in the course of the fourth month, it is always easily distinguishable in the lower part of the hypo gastric region, having then risen to the height of about three fingers-breadth above the pelvic brim. In the fifth month, the hypogastric region is completely filled ; the abdomen then acquiring a consitlerable rotundity in this situ ation. By the termination of the sixth month, the umbilical region also is filled, and the fundus uteri may be felt on a level with, or a little above, the navel. In the course of the rentaining three months, the uterus rises gra dually, until its fundus reaches the level of the ensiform cartilage. And this is very nearly the limit of its ascent, though it occasionally, and chiefly in first pregnancies, rises slightly above that point. In women who have a roomy pelvis, and in those cases where the natural form of the uterus is not altered by over-distension nor mai-position of the fcetus, there usually takes place, a few days or shortly before labour, a certain descent of the uterus, which has the effect of partially emptying the epigastric region, and relieving it from the pressure Nrhich it had sustained, especially during the last month.
The direction which the uterus takes in rising from the pelvis into the abdominal ca vity, is determined by various circumstances; and it is interesting to observe in what way the addition of so large a body as the fully developed uterus to the already occupied ab domen, is provided for, without any of the viscera suffering injurious pressure, and with out that impeditnent to the circulating and respiratory systems, which, in the absence of such a provision, must inevitably take place.