UTERUS (DEVELOPMENT). 



(J 19 



therefore occupy a position midway between 

 the spinal column and the posterior uterine 

 wall. The pressure of the sacral promontory, 

 and of the lumbar vertebrae, will still give to 

 the uterus a forward tendency, which, on the 

 other hand, will be prevented from becoming 

 excessive by the elasticity of the front walls 

 of the abdomen. If these have not been pre- 

 viously much distended, the fundus glides 

 upwards, and ultimately fills the epigastric 

 hollow ; but if the abdominal walls have been 

 much relaxed, as by frequent child-bearing, or 

 if the pelvis is much deformed, the fundus 

 uteri is usually turned directly forwards, or 

 even downwards. 



At the end of pregnancy, the whole of the 

 fore part of the abdomen is occupied by the 

 uterus ; on either side lie the ascending and 

 descending colon ; the transverse arch, to- 

 gether with the omentum and stomach, fill the 

 space between the fundus of the uterus and 

 the diaphragm, while the rest of the abdomi- 

 nal viscera lie laterally and posteriorly to its 

 hinder wall. 



Thus it results, that in pregnancy, and espe- 

 cially in its last stages, no injurious pressure 

 is exercised, either upon the great vessels, the 

 aorta and vena cava, or upon the intestines, 

 liver, or stomach, svhilst the descent of the 

 diaphragm, and, consequently, the act of 

 respiration, is not materially impeded, and 

 space is left for the bl idder and rectum to 

 perform their appropriate acts. 



The situation and direction of the pregnant 

 cervix, are necessarily affected by the increase 

 of the principal organ, as well as by its con- 

 tents. So long as the weight of the uterus 

 causes it to descend lower into the pelvic 

 cavity, as in the second and third months, the 

 cervix is more readily reached, lying in the 

 lower part of the hollow of the sacrum ; but 

 when the greater part of the uterus lies, as it 

 docs at a more advanced period, above the 

 pelvic brim, the cervix is felt with greater 

 difficulty, being more withdrawn from the 

 entrance of the vagina. If the lower segment 

 of the uterus is more than usually spread out, 

 as in transverse presentations, or in the case 

 of twins, or of excessive distension by liquor 

 amnii, then the cervix and os are drawn up 

 so high as sometimes to be quite beyond 

 the reach of an ordinary finger ; or, if the 

 pelvis is very narrow, or the abdominal walls 

 so lax as to cause the falling forward of the 

 womb, the cervix will be equally beyond 

 reach, and in these cases no part of the 

 uterus can be said to be within the pelvic 

 cavity. On the other hand, where the pelvis 

 is unusually roomy, and the vagina and liga- 

 ments are lax, the cervix may lie immediately 

 upon the perineum, or even project beyond 

 the orifice of the vulva. In most cases the 

 cervix lies lowest in the pelvis at the earlier 

 and latter periods of pregnancy, and highest 

 about and after the time of quickening. Its 

 projection into the vagina is not always in the 

 direction of the median line, but is more often 

 inclined to the left side, as that of the fundus 

 is towards the right. This obliquity in the 



position of the uterus may be caused by an 

 unequal length of the ligaments, or more com- 

 monly by the projection of the lumbar verte- 

 bra, which naturally gives to the body of the 

 organ an inclination towards one or other 

 side. 



Alterations in tf/e special coats and tissues. 

 The I'critoiieu-ni is that coat which suffers the 

 least alteration during pregnancy, yet the 

 changes which it exhibits are not inconsider- 

 able. They consist chiefly in a simple mul- 

 tiplication of the component elements of the 

 tissue, whereby it is enabled to keep pace 

 with the enormous rate of growth of the 

 uterus, so as still to invest all those portions 

 which were covered by peritoneum in the un- 

 impregnated state. During this process of 

 growth, the membrane does not become at- 

 tenuated, as would be the case if it suffered 

 mere distension, but its thickness is rather 

 increased, so that the addition of new matter 

 must be in the aggregate very great. 



Dr. W. Hunter imagined that this invest- 

 ment of the gravid uterus was accomplished 

 by an unfolding of the layers of the broad 

 ligament, for he asserts that, " in proportion 

 as the circumference of the uterus grows 

 larger, the broad ligaments grow narrower, 

 their posterior lamella covering the posterior 

 surface, and their anterior lamella covering 

 the anterior surface of the uterus itself." He 

 arrived at this conclusion from observing the 

 altered relative situation of the appendages, 

 and their appearance of clinging to the sides 

 of the uterus in advanced stages of pregnancy. 

 But the latter circumstance is due to the arch- 

 ing of the fundus, already described, which 

 gives to the appendages a downward direction ; 

 while that the broad ligament does not dis- 

 appear, as Dr. Hunter asserts, may be shown 

 by measuring the ate, or cutting them off, 

 and comparing them with the san e parts in 

 the unimpregnated state, when little or no 

 difference in respect of dimensions will be 

 found between them in the two conditions. 



Beneath the peritoneum of the gravid ute- 

 rus is always found a large development of 

 strong fibrous lix.tiit; arranged in irregular 

 cords and bundles. These sub-peritoneal 

 fibres serve to strengthen the coats, and pro- 

 bably greatly contribute to prevent rupture of 

 the organ, especially during labour. 



The muscular or middle coat. The tissues of 

 which this coat is composed, together with 

 their mode of arrangement in the unimpreg- 

 nated uterus, have been already fully de- 

 scribed. And it is to an increase of these, 

 but especially of the vascular and muscular 

 elements, that the enormous growth of the 

 uterus during pregnancy is chiefly due. This 

 growth consists partly in a greater develop- 

 ment of the already existing structures, and 

 partly in new formations. 



Tne growth of the contractile fibre cells is 

 here of especial interest. The elements of 

 this tissue have been shown to consist, from 

 infancy onwards, of fusiform fibre cells, inter- 

 mixed with the round, oval, and elongated nu- 

 clei (Jig. V34-.), which constitute their embryoi.ic 



