PROFESSOR W. TURNER ON THE PLACENTATION OF THE APES. 
537 
into the more posterior placental lobe, and had insinuated itself between the foetal villi, 
where it formed a continuous network extending from the placental layer of the 
decidua to the stratified arrangement of sub-chorionic cells covering the placental 
surface of the chorion. This network of red injection was not contained in cylindri- 
form tubes, so that it had no definite pattern, but exhibited an irregular anastomosing 
arrangement. In those parts of the lobe where the injection was most perfect, the 
stems, branches, lateral and terminal bud-like offshoots of the villi were seen to be 
surrounded by the red injection which was separated from the blue injection, occupying 
the umbilical vessels of the villi, by the cellular investment of the villi and by the more 
peripheral part of their delicate connective tissue. The sj)aces occupied by this net- 
work of red injection are, I believe, those through which the maternal blood flows in 
the living placenta. That they are not artificial channels produced in the act of 
injection is I consider established by their free communication with the utero-placental 
veins, and from the fact that they were filled with but a slight pressure on the piston 
of the injecting syringe. These spaces were not of uniform diameter; as a rule they 
were not equal to the transverse diameter of the villi, but sometimes they were of 
equal width, and occasionally even were wider than the villi. The width of the 
channels through which the injection, or the maternal blood, flowed would un- 
doubtedly, within certain limits, vary with the pressure on the blood or injection 
contained in the maternal vessels. I could not satisfy myself that the spaces con- 
taining the red injection were enclosed by a definite membrane, continuous with the 
wall of the uterine arteries or veins, and separating the injection from the cellular 
investment of the villi. All that I saw was in favour of the view that the injection, 
and consequently the maternal blood in the living animal, was in direct contact with 
the cellular investment of the villi, the sub-chorionic cellular covering of the placental 
surface of the chorion, and the cellular surface of the placental layer of the decidua 
serotina. It is not unlikely, however, that at the relatively large crescentic openings 
of communication between the utero-placental veins and the spaces in the interior of 
the placenta, the lining membrane of the vein is prolonged for some distance along 
the placental surface of the placental layer of the decidua. 
Comparison of the Placenta of the Ape with that of the Unman Female. 
In the course of my description of the gravid uterus and placenta of Macacus 
cynomolgus I have incidentally referred to some points of correspondence with, or 
difference from, the human gravid uterus and placenta, but it may not be uninter- 
esting to make a more detailed comparison of the one with the other. More 
especially is it advisable to compare the minute structure of the organs, for up to this 
time satisfactory material for doing so has not been in the possession of anatomists. In 
the course of this comparison I shall refer to a number of original observations on the 
human gravid uterus and placenta, many of which, though incorporated in one of my 
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