656 



UTERUS AND ITS APPENDAGES. 



circumference, and are very numerous, large, 

 and close set, in the decidual fold at the base, 

 all round the line of apparent reflexion. 



Numerous flat vessels, obviously veins, 

 terminating in minute subdivisions, are seen 

 ramifying over the whole surface, but be- 

 coming very scanty, or ceasing near the cen- 

 tral point. They are continuations of similar 

 vessels, which are still more conspicuous 

 upon the parietal decidua. The capillaries 

 in which these vessels terminate are exceed- 

 ingly numerous, and may be sometimes seen 

 deeply injected with blood. This is rendered 

 the more conspicuous when the congestion 

 is unequal, so as to form patches of a bright 

 pink, alternating with other portions of a pale 

 flesh colour. 



The internal surface of the foetal chamber, 

 after the ovum has fallen out, or has been re- 

 moved, presents a slightly uneven appearance, 

 occasioned by numerous very shallow pits or 

 depressions, occurring in close-set groups, and 

 resembling, upon a small scale, the areolae 

 upon the inner surface of the heart. 



When the body of the embryo begins to 

 acquire length, the entire ovum exchanges 

 the spherical for the slightly oval form, and to 

 this the foetal chamber also becomes adapted. 

 Such is found to be the form of the foetal 

 chamber, sometimes in the latter half of the 

 first, but generally during the second month, 

 and from this period onwards the ovate figure 

 prevails. 



In the latter part of the first month, or at 

 latest in the beginning of the second, the ovum, 

 previously lying loose in the foetal chamber, 

 begins to be attached to the walls which sur- 

 round it. This attachment is effected by the 

 extremities of the villi, which from the first 

 equally surround the chorion, everywhere be- 

 coming attached to the little pits and anfrac- 

 tuosities upon the inner surface of the foetal 

 chamber just described. In this way the em- 

 bryo, surrounded by its amnion and chorion, 

 becomes securely anchored in the midst of .its 

 little chamber, through the instrumentality of 

 the villi, which, spreading in all directions, 

 may be compared to the rays of the geometric 

 spider's web. 



Thus to receive, to protect, and support 

 the ovum, and to prevent its escape from the 

 uterus, appears to be the first object of the 

 formation by the reflected decidua of a sepa- 

 rate foetal chamber (fig. 453.). 



Ultimately, as the ovum grows, the base of 

 its chamber expands, and here takes place a 

 more dense and rapid growth of decidua. 

 This is the part commonly termed the decidua 

 serotina. Here the chorion villi, which now 

 form large ramified groups, attach themselves, 

 and from the margins of the collections of 

 sulci just described, into which the villi pene- 

 trate, and which are now much extended, 

 there proceed offsets or dissepiments of de- 

 cidual structure. These dip down between 

 the groups of villi sometimes as far as the 

 surface of the chorion, and divide that 

 which was formerly one continuous collec- 

 tion of ramified chorion fringes, into the 



separate lobes which characterise the mature 

 placenta. 



One or two points remain to be more ex- 

 plicitly stated. It may be asked, how does 

 the ovum gain the interior of the foetal cham- 

 ber, or, in other words, how is the decidua 

 reflexa formed around it ? In reply to this, 

 little beyond conjecture can be offered. Of 

 the numerous explanations which have been 

 attempted, few are found to meet all the pe- 

 culiarities of the case. It is most probable 

 that either the ovum becomes embedded in 

 some of those folds of decidua which are 

 found in it at an early period of pregnancy, 

 and so the decidua becomes built up around 

 it, as Sharpey and Coste suppose. Or, as it 

 appears to me more likely, the ovum, on first 

 reaching the uterine cavity, drops into one of 

 the orifices leading to the utrirular follicles, 

 and in growing there draws around it the 

 already formed, but soft and spongy decidua 

 constituting the walls of the cavitv. The 

 chief support for such a conjecture, beyond 

 its apparent probability, is the fact ascertained 

 by Bischoff, who, in one case in the guinea- 

 pig, found the ovum in precisely this situation 

 at the bottom of a uterine follicle.* 



The entrance of the ovum into the decidua 

 being supposed, the rest of the growth of the 

 reflexa is easily followed. The ovum now, in 

 enlarging, raises the walls of the chamber, in 

 which it lies, just as the skin becomes raised 

 by the accumulating contents of a subcuta- 

 neous abscess. The process is probably in 

 part purely mechanical, and in part in the 

 nature of an excentric hypertrophic growth ; 

 for the actual substance of the chamber is 

 much increased beyond the material of which 

 it was at first composed. That some of this 

 is borrowed from the parietal decidua, is very 

 probable from the number of orifices of utri- 

 cular glands seen upon its surface, which 

 serve to show that the decidua reflexa is so 

 far formed out of pre-existing structures ; but 

 much is also due to the further development 

 of the elemental decidual tissues ; and to the 

 growth of these, the large vascular supply, 

 which the reflexa at first receives, doubtless 

 contributes. The little point, or umbilicus, 

 observed sometimes at the upper pole of the 

 foetal chamber, may mark the spot at which, 

 upon either of the foregoing hypotheses, the 

 ovum first entered the decidua. 



Another question which has never been 

 satisfactorily determined, relates to the ulti- 

 mate fate of the decidua reflexa. Dr. Hunter, 

 from observing that, at the time of birth, only 

 one layer of decidua can be found upon the 

 secundines, supposed that, after a certain pe- 

 riod of pregnancy, the decidua vera and re- 

 flexa, having come into contact, united to 

 form one membrane. Doubting this explana- 

 tion, I have made many observations, with a 

 view to settle this point ; and from these I 



* While these sheets are passing the press, I have 

 received the last part of Otto Funke's " Lehrbuch 

 der Physiologic," 1857, in which the same sugges- 

 tion is offered, exemplified by the same case, which, 

 indeed, is the only one yet known. 



