540 Proceedings of the Royal Society 
into, or in any way to communicate with, the pits within the coty- 
ledon itself. 
The foetal cotyledons consisted of numerous villi, which collec- 
tively formed a hall-like mass, occupying the concavity of the 
maternal cotyledon. Each villus consisted of a main stem, which 
gave off a tuft or cluster of spatulate branches. The villi entered 
the maternal pits and branched along with them, so that every 
compartment was occupied by a branch of the villus ; hut there was 
necessarily no great divergence of these branches from the main 
stem. At their deeper end these spatulate branches gave off 
slender terminal offshoots. The villi were formed of gelatinous 
connective tissue, in which very distinct fusiform and stellate cor- 
puscles were arranged in an anastomosing network. At the peri- 
phery of the villus was a layer of flattened cells, with small but 
distinct nuclei arranged so as to form an epithelial-like investment. 
The umbilical vessels ramified within the villus and formed net- 
works of capillaries. The villi were in close contact with the 
epithelial cells lining the maternal pits. Owing to the inversion of 
the free edge of the maternal cotyledon and the radiated arrange- 
ment of the pits, with their contained villi, it was impossible to 
disengage the maternal and foetal cotyledons from each other with- 
out drawing away with the foetal villi portions of the maternal 
cotyledon. I invariably found that, in drawing the foetal villi out 
of their compartments, flakes of epithelial cells accompanied them, 
which showed how readily this element of the maternal tissue is 
shed. During parturition, however, when the parts are relaxed, 
the disengagement of the two structures is necessarily more easily 
accomplished. 
In the cow the maternal cotyledons differed in form from those 
in the sheep. They were fungiform or umbrella-shaped, and were 
connected to the uterine wall by a broad neck, around which the 
uterine mucosa was prolonged as far as the border of the umbrella. 
The whole convex surface of the cotyledon was riddled with pits, 
which passed vertically into its spongy substance, and divided into 
smaller compartments in the deeper part of the cotyledon. Pro- 
jecting from the wall of each pit were delicate bands, visible to 
the naked eye, arranged as a rule in a vertical direction, and in the 
intervals between these bands the wall was perforated by nume- 
