762 Proceedings of the Royal Society 
be the character of the arrangement. The chorionic villi were seen 
in these sections to be cut across longitudinally, obliquely, and trans- 
versely, and the villi were not in contact with each other by their 
surfaces, hut separated by intermediate freely-communicating spaces, 
filled with coloured gelatine. These spaces constituted the intra- 
placental maternal sinus vascular system. Thin sections examined 
with high powers showed multitudes of red-blood corpuscles lying 
in the coloured gelatine, which corpuscles had undoubtedly been 
in these sinuses before the injection had been passed into them, 
and from their position were the corpuscles of the maternal blood. 
The ready manner in which the injection flowed into the intra- 
placental sinuses, either when passed directly into the placenta, 
or through the artery, or through the vein, the regularity and 
uniformity of the pattern produced by the injection when set, 
and the abundance of blood corpuscles present in the sinuses, 
mingled with the injection, seemed to the author to substantiate 
the view that these sinuses are a natural system of intercom- 
municating spaces for the transmission of the maternal blood 
through the interior of the placenta; and not as some have main- 
tained, artificially produced by the extravasation of injection from 
the uterine vessels into the placenta. 
The author then proceeded to describe the structure of the 
chorionic villi, to show their relations to the decidua serotina and 
the decidual bars which pass into the interior of the placenta, and 
to discuss the views which have been advanced, whether the villi 
hang naked in the maternal blood, or whether they are invested 
either by a prolongation of the lining membrane of the maternal 
blood-vessels, or by the cells of the decidua, or by both. 
The following Gentleman was admitted a Fellow of the 
Society : — 
Rev. Hugh Macmillan, LL.D. 
