UTERUS- (DEVELOPMENT). 



653 



upon the arrival of the ovum within the ute- 

 rine cavity are, in the human subject, as yet 

 unknown. Direct observation of the earliest 

 stages are still wanting, and, unfortunately, the 

 difference between these first steps in the 

 mammalia (except Quadrumana) and man is 

 so considerable, that only a limited aid can be 

 derived from comparative observation. The 

 ovum, when first found in the human uterus, 

 is lodged in a small closed cavity, forming a 

 continuous structure with the decidua which 

 lines the rest of the uterine walls. In this 

 little chamber, which may be formed at any 

 part, but is most frequently seen near one or 

 other of the tubal orifices, the little spherical 

 ovum lies loose and unattached. In various 

 examples which have been preserved and 

 figured by different authors of the decidua at 

 tfais stage, the size of this chamber varies from 

 that of a pea to a hazel nur, and this size it 

 acquires in the second week. 



The walls of the cavity containing the 

 ovum, and those forming the lining membrane 

 of the uterus, are nearly alike in appearance 

 and texture. They both consist of decidua, 

 the former constituting the decidiirt reflexa, 

 the latter the decidua vera of Dr. W. Hunter. 

 For greater distinctness, those names are 

 sometimes exchanged for decidua e/iorii or 

 ovu/i, and decidua uteri. The latter, accord- 

 ing to a suggestion of Dr. M. Baillie, is also 

 occasionally termed parietal decidua. 



At this time all the uterine tissues have 

 begun to expand and grow, and the uterine 

 cavity, the walls of which were previously 

 nearly in contact, to enlarge after the manner 

 which in pathology constitutes eccentric hy- 

 pertrophy. But, according to the foregoing 

 description, this cavity now no longer forms 

 one, but two compartments, the one partly 

 inclosed within the other. 



Of these two chambers, the newly formed 

 and smaller one contains and supports the 

 ovum, and subsequently the foetus. It may 

 therefore be termed the foetal chamber ; the 

 other constitutes the original cavity of the 

 uterus, and may be distinguished as the ute- 

 rine chamber ; according to the views of 

 Breschet, it is the hydroperionic cavity. As 

 the foetal chamber enlarges, and the decidua 

 reflexa becomes more expanded in consequence 

 of the growth of the contained ovum, it gra- 

 dually encroaches upon and finally obliterates 

 the uterine chamber, which can no longer be 

 distinguished as a separate cavity after the fifth 

 or sixth month of gestation. 



It will be necessary to examine separately 

 the general characters of these two decidual 

 coats. That which lines the uterine cavity 

 may be first noticed. The parietal decidua, 

 at the very earliest period of pregnancy in 

 which it can be examined, forms a soft and 

 spongy layer, 1 2" in thickness. That surface 

 which looks towards the uterine cavity is ele- 

 vated into numerous projections, which may 

 be roughly compared to the cerebral convolu- 

 tions, though relatively much Hatter and less 

 regular than these; between them are nume- 

 rous little furrows or channels. The whole 



surface, both in the sulci and elevations, is 

 covered by numerous minute perforations, 

 corresponding with those formerly described 

 as the orifices of the uterine glands in the 

 unimpregnated uterus. But these orifices, 

 from being enlarged, may now be easily dis- 

 tinguished by the unaided eye. They give to 

 the surface a fine cribriform aspect. All these 

 characters are more or less observable aUo 

 in the decidua lining the uterus, in cases of 

 extra-uterine (tubal) gestation. Along the 

 marginal lines formed by the angles of the 

 cavity, where the decidua is always thinnest, 

 these apertures are large and expanded, but 

 in the elevated spots they are often closed, 

 apparently from lateral pressure, occasioned 

 by the rapid growth of structure. 



When early abortion takes place, the whole 

 lining of the uterus, including the decidua 

 reflexa, is often thrown off entire, forming a 



Fig. 450. 



The entire decidun or lining membrane of the uterus 

 cast off in abortion. (After W. Hunter. ~) 



A portion of the specimen has been cut away to 

 show the interior, which had formed the uterine 

 cavity. The slight elevations upon this surface are 

 very characteristic of the decidua in this condition. 

 The outer surface is rough and flocculent. The 

 foetal chamber is in process of formation in the 

 upper part of this specimen, near one of the tubal 

 orilices. The ovum having at this time no adhesion 

 to the walls of the chamber, has dropped out of it. 

 Bristles are introduced at the orifices corresponding 

 with the Fallopian tubes, and pass out at the 

 internal os uteri, the cervix not contributing to 

 form the decidua. 



cast of the uterine cavity. If this occurs in 

 the first fortnight of gestation, the mass re- 

 tains the triangular form of the uterus. In 

 each of the three angles is generally found an 

 aperture corresponding with the points at 

 which the membrane had been torn off from 

 its continuity with the lining of the Fallopian 

 tubes and cervix uteri. 



The outer, or dorsal surface of the sub- 

 stance expelled, is always rugged. It exhibits 

 numerous little papillary or club-shaped ele- 



