344 MINOT. [ Vou. IL 
to the space between two folds, which alone participate in the 
formation of the placenta; accordingly we may designate them 
as the placental folds. In the region of the swellings the 
placental folds are already hypertrophied, and form a marked 
contrast to the opposite side, where the folds have completely 
disappeared, and their glands have become shorter and some- 
what contorted; the two lateral folds are intermediate in ap- 
pearance. In the placental folds there is a great increase in 
the connective tissue, which consists solely of anastomosing 
cells, forming a loose meshwork of very granular protoplasm, of 
which only a small amount is accumulated around each nucleus. 
Described in other words, the cells are small, granular, with long 
processes continuous with those of adjacent cells. The glands 
extend only a short and nearly uniform distance down from the 
surface of the folds; the glands themselves are somewhat 
dilated ; their epithelium stains deeply ; its free surface is quite 
irregular; the nuclei are greatly increased in number, and lie 
crowded throughout the whole thickness of the layer; the nu- 
clei are round or oval in outline, with a well-marked reticulum 
densest superficially. In many places the nuclei are grouped, 
three, four, or five together, and sometimes one can distinguish 
a distinct outline around the group. These appearances I in- 
terpret as evidence that the nucleus of each cell proliferates, 
rendering the cell multinucleate. The blood-vessels are like- 
wise hypertrophied in the placental folds, and to a less extent 
in the adjacent folds, but not at all in the folds opposite the 
placenta. In the placental folds there are larger blood-vessels 
running for the most part longitudinally, and all situated in the 
zone next the muscularis ; between this zone and the glandular 
layer, the blood-vessels are, on the contrary, all of small calibre, 
most of them taking a more or less radial course, and lying ap- 
proximately in the plane of the transverse sections. All the 
blood-vessels of the mucosa have, so far as I have observed, the 
character of capillaries, for they consist of merely an endothe- 
lium without adventitial or muscular envelope, although some 
of them are many times the diameter of ordinary capillaries. 
The blood-vessels of the placenta of the Guinea pig are stated 
by Creighton, 77a, p. 544, to have the same character. There 
is a single layer of connective tissue cells condensed around the 
vessels, and representing the commencement of the perivascu- 
