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PROFESSOR W. TURNER ON THE PLACENTATION OF TPIE APES. 
Structure of the Placenta. 
Each lobe of the placenta was half an inch thick at its centre, but was much 
thinner at the circumference of the disc. On making a section into its substance, 
it was seen to have a spongy appearance similar to the human placenta. Its foetal 
surface was limited by the chorion ; its uterine surface by a thick layer of modified 
uterine mucous membrane homologous with the decidua serotina of the human 
gravid uterus (fig. 5). The stems of the villi arose at intervals of from p^-th to -^-ths 
of an inch from each other. Each stem was, as a rule, so thick that it could be 
readily followed out with the naked eye or a simple lens, and be traced through the 
substance of the placenta to be attached to the hillock-like elevations of the decidua 
to be presently described: The stems were usually oblique in their direction, and 
it was not uncommon to see one, notwithstanding the branches which arose from it, 
reaching the decidua without experiencing any material diminution in size. In their 
course the stems of the villi gave off numerous branches, which divided and subdivided 
until they ended in the lateral and terminal bud-like offshoots of the villi (fig. 6). These 
buds varied in shape and size, some being elongated and cylindriform, whilst others 
were short and stunted, and it was by no means uncommon to find the latter arise in 
pairs. Branches of the umbilical vessels of considerable size, derived from the vessels 
in the chorion, were prolonged into the stems of the villi, and from them offshoots pro- 
ceeded into the branches of the villi. The lateral and terminal buds contained a 
looped arrangement of capillaries. The loop might be single, or twisted so as to 
have a double coil, and the capillaries from one bud, more especially when the buds 
arose in pairs, might pass from one bud into the adjacent one. Sometimes the capil- 
laries formed a network. 
The placental chorion consisted of connective tissue distinctly fibrillated, and with 
fusiform connective tissue corpuscles. In many sections through it I observed rows of 
cells, arranged parallel to and at no great distance from the surface on which the 
amnion rested. These intra-chorionic cells did not form a continuous layer, but were 
found in patches (fig. 8). Sometimes they were in a single row, at others in two or 
more. They were elliptical, ovoid, rounded, or somewhat polygonal in form, with 
granulated protoplasm, and varied in size from a white blood corpuscle to about twice 
that size. The cells in each group were closely related to each other. They were 
quite distinct, both in position and appearance, from the amniotic epithelium. The 
fibrillated connective tissue was prolonged into the stems of the villi ; but in the finer 
branches, and in the lateral and terminal buds, the tissue became so delicate that a 
differentiation into fibrillse could not be recognised. A partially injected network of 
capillaries, continuous with the smaller tortuous umbilical vessels, was situated in 
the connective tissue of the chorion in the intervals between the origins of the stems 
of the villi, and formed an extra- villous capillary plexus. 
The surface of the chorion next the interior of the placenta was covered by a strati- 
