GO 
DR. LEE ON THE STRUCTURE OF THE HUMAN PLACENTA, 
der filaments running* in various directions. The placenta thus consists solely 
of a congeries of the umbilical vessels, covered on the foetal surface by the 
chorion and amnion, and on the uterine surface by the deciduous membrane, 
and inclosed between these membranes ; it adheres to the fundus, or some 
part of the uterus by innumerable flocculent fibres and vessels. 
On detaching the placenta carefully from the uterus, the deciduous mem- 
brane is found to adhere so closely to the umbilical vessels which it covers, 
that it is impossible to remove it without tearing these vessels. With the 
fibres uniting the placental decidua to the uterus are mingled numerous small 
blood-vessels, proceeding from the inner membrane of the uterus to the deci- 
dua ; and these vessels, though more numerous at the connexion of the pla- 
centa with the uterus, exist universally throughout the whole extent of the 
membrane. There is no vestige of the passage of any great blood-vessel, 
either artery or vein, through the intervening decidua, from the uterus to the 
placenta; nor has the appearance of the orifice of a vessel been discovered, even 
with the help of a magnifier, on the uterine surface of the placenta. This sur- 
face of the placenta deprived of the deciduous membrane presents a mass of 
floating vessels, its texture being extremely soft and easily torn ; and no cells 
are discernible in its structure, by the minutest examination. 
At that part of the surface of the uterus to which the placenta has been 
adherent, there are observable a great number of openings leading obliquely 
through the inner membrane of the uterus, and large enough to admit the 
point of the little finger : their edges are perfectly smooth, and present not 
the slightest appearance of having been lacerated by the removal of the pla- 
centa. In some places they have a semilunar or elliptical form, and in others 
they resemble a double valvular aperture. Over these openings in the inner 
membrane of the uterus, the placenta, covered by deciduous membrane, is 
directly applied, and closes them in such a manner that the maternal blood, as 
it flows in the uterine sinuses, cannot possibly escape either into the cavity of 
the uterus, or into the substance of the placenta. The above appearances on 
the inner surface of the uterus have been accurately represented by Rxederer ; 
from whose work fig. 1. of Plate I. is taken. 
When air is forcibly thrown either into the spermatic arteries or veins, the 
whole inner membrane of the uterus is raised by it ; but none of the air passes 
