542 Proceedings of the Royal Society 
whilst from others small portions were taken and teezed out with 
needles. In the examination, a magnifying power of 320 diameters 
was employed. Quantities of cells, having the form and appearance 
of the epithelial cells already described, were seen to be inter- 
mingled with the foetal villi. In some cases small patches of cells 
were seen lying free in the spaces between the villi, but more fre- 
quently the cells were isolated. In a few instances I saw groups of 
such cells in immediate contact with the terminal villi, as if they, 
in being drawn out of the compartments in the maternal cotyledon, 
had pulled an envelope of epithelial cells along with them. 
When the cotyledons of the shed placenta of the cow were 
examined microscopically, quantities of granular debris were to he 
seen floating in the fluid in which the specimens were placed. 
Along with these granules were small flakes of protoplasm; rounded 
or ovoid bodies, with distinct outlines looking like free nuclei ; and 
large cells composed of granular protoplasm, containing one, two, 
or three nuclei, having the anatomical characters of maternal epi- 
thelial cells. 
The amount of debris and of decidua cells varies considerably in 
the different slides which I examined; in some being so abundant 
as to render the fluid in which the specimen was examined quite 
turbid, whilst in others only slight traces were to be recognised. 
From these observations I am of opinion that, both in the sheep 
and cow, the cotyledons of the foetal placenta carry away with 
them, during the act of parturition, a portion of the maternal struc- 
ture, so that in these animals, and presumably in other ruminants, 
the placenta is deciduate. So far as my observations have gone, I 
have only detected the epithelial element of the uterine mucosa, or 
the cells of the decidua serotina, intermingled with the foetal villi; 
but from the bloody state of the external parts of the ewe, for some 
hours after the birth of the lamb, I think it not improbable that 
the disruption of some of the maternal cotyledons has been deeper 
than a mere epithelial shedding, — that the maternal vessels have, 
in some places at least, been torn across, so as to give rise to the 
haemorrhage. 
From the observations which I have made on the structure of 
the placenta in many of the Mammalia, both in the deciduata as 
well as in the so-called non-deciduata, I am of opinion that the 
