290 PROFESSOR TURNER ON THE 
Comparison of the Placentation of the Seals with that of the Carnivora. 
As the Seals possess, like the true Carmvora, a zonary placenta, and as the 
development of the placenta in the seal, at least in the early stages, is in all 
probability similar to that in the Carnivora, it may not be out of place to examine 
the placenta in some genera of the latter order, and to compare its structure 
with that of the seals. I have examined, with this object, the structure of the 
placenta and gravid uterus in the Cat, Bitch, and Fox, and as I have observed 
it at various periods of gestation in the cat, I shall commence by describing the 
placenta in that animal. | 
In the earliest impregnated Cat’s uterus, which I have examined, the compart- 
ments were ovoid, and the long diameter of each measured along the arc did not 
exceed -8,ths inch. When a compartment was opened the chorion separated 
from the uterus with great readiness, and exposed the uterine mucosa. At 
each pole of the compartment an area jth inch in its long diameter was smooth, 
but the rest of the mucosa was hypertrophied, spongy, swollen, and elevated — 
above the smooth polar portions, and formed the placental area. The placental 
area possessed on its surface an extremely delicate reticulation, many of the 
strands of which had a sinuous direction. It was thickly studded with minute 
orifices barely visible to the naked eye, but easily seen with a pocket lens. © 
These orifices were the mouths of the pits or crypts in which the villi of the 
chorion had been lodged. A few of these openings were two or three times 
larger than the rest. The appearance which I saw in the cat is evidently similar 
to that figured by Dr SHarpey in the bitch (fig. 211),* and by BiscHorr in 
the same animal (fig. 48, A),t though, as will be seen further on, I interpret 
its mode of production in a different manner from those anatomists. 
The crypts passed vertically into the spongy substance, and when vertical — 
sections were made through it, they were seen to be separated from each other 
by trabeculee ; the chief beams of which lay vertically, and when they reached 
the free surface formed the strands of the reticulum already described (fig. 11). 
The vertical trabeculz were connected together by others directed obliquely or 
in a sinuous manner, and these lateral connections were especially seen about 
midway in their length. Hence, not only on the surface, but when horizontal ~ 
sections were made through the placental area, a reticulated arrangement was — 
seen, and the crypts constituted the interstices of the reticulum (fig. 12). As 
these trabeculee were formed of the thickened mucous membrane of the placental — 
area, they were necessarily composed of the somewhat modified tissues of that 
membrane. On the surface was a definite layer of epithelium, the cells of which — 
were short columns, with distinct, circular, or ovoid brightly refracting nuclei. — 
* Baly’s Translation of Miiller’s Physiology, note p. 1576. 
t+ Entwicklungs-geschichte des Hunde Eies, 1845. 

