294 PROFESSOR TURNER ON THE 
blood-corpuscles. It is possible that these dilatations may have been to some 
extent due to the force employed in filling the maternal vessels with injection ; 
but this will not, I think, account for the whole extent of the dilatation. The 
vessels of the capillary network of the foetal villi were injected with a blue 
colour and showed no dilatation; and the contrast between the two systems 
of vessels within the organ was well seen both in horizontal and vertical sec- 
tions (figs. 13, 14). 
The placenta of a cat, shed in the ordinary course of parturition, was 
covered on its uterine surface by a layer of soft yellowish-white tissue, which 
was smooth and uniform in character, and was without any flocculent, ragged 
processes, projecting from it. This layer was the deciduous serotina, and from 
it laminee and trabeculz passed into the substance of the placenta, which had 
a similar sinuous arrangement and relation to the foetal villi as in the placenta 
at half-time. Examined microscopically, the vascular connective tissue of the 
serotina, with its epithelial investment, was recognised, but as it was not possible 
in a detached placenta to inject the maternal blood-vessels, their disposition 
could not be made out. I examined thin sections through the serotina for the 
presence of utricular glands. I saw indistinct appearances of tubes trans- 
versely or obliquely divided, which might be interpreted as tubular glands; but 
the aggregation of cells within and around them was so great that it was 
difficult to speak positively on this point. The chorionic system of feetal 
blood-vessels was injected, and the leaf-like villi, with their remarkable compact 
capillary plexus, were readily seen. On examining with a pocket lens the 
uterine surface of the serotina, many minute, rounded, scattered holes were 
seen in it, through each of which a terminal bud of a leaf-like villus projected, 
so as to reach the uterine surface of the placenta. These buds were often 
clavate in form, and contained a capillary plexus continuous with that of the 
body of the villus. It is clear, therefore, that when the placenta of the cat is 
shed at the time of parturition, a continuous layer of serotina, interrupted only 
by these minute orifices, is shed along with it. 
The presence of a layer investing the uterine surface of the cat’s placenta, 
analogous to the caducous layer of the human placenta, was distinctly recog- 
nised by Escuricut, who also described the thin, perpendicular, flexuous lamin 
of maternal structure passing through the entire thickness of the organ, and 
investing the foetal villi as if with sheaths.* Though Escuricur was at first 
inclined to the view that the layer investing the uterine surface of the placenta 
was nothing else than the mucous tissue of the uterus, further consideration led 
him to state that it altogether differed from that tissue. But he also came to 
the conclusion that the mucous tissue was left entire in the placental zone, 
exhibiting only torn and broken-off vessels. 
* De Organis, &., pp. 14, 18. 

