562 PROFESSOR W. TURNER ON THE PLACENTATJON OF THE APES. 
placental veins could be seen. It is clear, therefore, from this specimen, as well as 
from the appearance presented by the placenta of the Baboon, that, when the placenta 
is separated, a portion of the decidua remains attached to the wall of the uterus, and 
that another portion peels off with the placenta ; hence, to use the terms employed by 
Dr. Bolleston, there is both a deciduous and a non-deciduous serotina. 
As it was desirable to make quite certain that the vessels I have described in the 
whole series of placentas as utero-placental veins, were veins and not arteries, I 
directed my assistant, Mr. A. B. Stirling, to pass a red injection into the uterine 
arteries of Cercocebus fuliginosus and a blue injection into the uterine veins, so as to 
inject the vessels belonging to the attached lobe of the placenta, and enable me 
readily to discriminate the one set of vessels from the other. I then found on care- 
fully detaching the lobe from the placental area of the uterus that the vessels corre- 
sponding to those which I have throughout this Memoir described as utero-placental 
veins contained the blue injection, so that the accuracy of my interpretation of their 
venous nature was thus established. But entering this same placenta were several 
vessels, which contained a red injection, and may therefore be fairly regarded as 
utero-placental arteries. Though smaller than the utero-placental veins, they were 
yet large enough to admit a pig’s bristle, and when slit open were seen to have a 
distinct orifice into the placenta, through which the foetal villi could be seen. Hence 
it is probable that the fine arteries, which I saw in the decidua serotina of Macacus 
cynomolgus (p. 536), were not for the placenta, but for the supply of the decidual 
tissue. 
By means, therefore, of these two placentae I have been able to establish much more 
definitely than in the placenta of Macacus cynomolgus the distinction between the 
utero-placental arteries and veins, and to show that each kind of vessel lias a free 
communication with the interior of the placenta, so as to provide for a free circulation 
of blood throughout the interior of the organ. 
In tearing away the non-pla, cental chorion of Cercocebus from the wall of the uterus, 
I observed a number of very tortuous arteries, filled with red injection, passing from 
the uterine wall to that layer of the decidua which remained attached to the chorion. 
These vessels were so slender as to appear to the naked eye not larger than fine 
threads. 
The outer surface of the chorion of the shed placenta of Cynocephalus was irre- 
gularly covered by a thin flocculent membrane, which was, as a rule, closely adherent 
to the chorion, though in places it was flocculent and partially separated from it. 
In its structure it consisted for the most part of white fibrous connective tissue, in 
which many fusiform corpuscles were situated. Occasional patches of polygonal cells, 
set together after the manner of an epithelium, were also seen. This membrane 
obviously represented the decidue reflexa of previous writers on this subject ; but for 
the reasons I have already advanced (p. 545), it is difficult to say how far the membrane 
was a decidua vera or a decidua reflexa. 
