AND ITS CONNEXION WITH THE UTERUS. 
61 
across the deciduous membrane into the placenta, nor does it escape from the 
semilunar openings in the inner membrane of the uterus, until the attachment 
of the deciduous membrane to the uterus is destroyed. There are no openings 
in the deciduous membrane corresponding with these valvular apertures now 
described, in the internal membrane of the uterus. The uterine surface of 
the placenta is accurately represented in fig. 2. Plate I. 
If a placenta be examined which has recently been separated from the uterus 
in natural labour, without any artificial force having been employed, its sur- 
face will be found uniformly smooth, and covered with the deciduous mem- 
brane ; which could not be the case, did any large vessels connect it with the 
uterus. The placenta in a great majority of cases is also detached from the 
uterus after labour, with the least imaginable force ; which would be impossi- 
ble if a union by large blood-vessels, possessing the ordinary strength of arteries 
and veins, actually existed. Besides, a vascular connexion of such a kind 
would be likely to give rise, in every case, to dangerous hemorrhage subsequent 
to parturition, a circumstance not in accordance with daily experience. 
Noortwych, Rcederer, Haller, Dr. W. and Mr. J. Hunter, and Dr. Donald 
Monro, do not appear to have examined the gravid uterus and its contents in 
the natural state of the parts, but after fluids had been forcibly injected into 
the hypogastric and spermatic arteries. The laceration of the deciduous 
membrane covering the orifices of the uterine sinuses followed this artificial 
process, as well as the formation of deposits of injection in the vascular struc- 
ture of the placenta, giving rise to the deceptive appearance of cells. That 
this took place in the examinations made by Rcederer* and Monro -j~, does 
not admit of dispute ; and the following facts render it more than probable 
that the Hunters were also misled, by the effects of artificial distention of the 
placenta, from the extravasation of the fluids forced into the uterine vessels. 
In the course of last autumn, the preparations of the gravid uterus in the 
Hunterian Museum at Glasgow were examined at my request by Dr. Nimmo ; 
and in none of them does it appear certain that any great blood-vessels pass 
from the uterus into cells in the placenta ; but in many the deposits of injection, 
causing the appearance of cells, were observed evidently to be the result of 
extravasation. No preparation in the collection seems to have been expressly 
* leones Uteri humani, Observationibus illustratse. J. G. Rcederer, 1759. 
f Essays and Observations, Physical and Literary, read before a Society in Edinburgh, 1754. vol. i. 
