PROFESSOR W. TURNER ON THE PLACENTATION OF THE APES. 
543 
The decidua vera in the human uterus is thicker than the mucous membrane of the 
unimpregnated uterus, and this thickening is always considerably greater in the 
earlier than in the later months of pregnancy. The superficial part of the membrane 
is comparatively compact, whilst the deeper part possesses a looser and more spongy 
character. The ciliated columnar cells, which form the epithelial covering of the free 
surface of the non-gravid membrane, disappear. The glands become expanded, and 
though they retain for a time their elongated tubular form, yet in the later months 
of pregnancy, in correlation with the growth of the ovum and the expansion of the 
uterine wall, they are so altered that the evidence of their presence is so much 
obscured that they are recognised with difficulty. 
The human gravid uterus at the fifth month, with its contained placenta, closely 
approximates in size to the gravid uterus of the Macacus cynomolgus, which forms the 
special subject of this Memoir ; and it may not be without interest to compare the 
structure of the human decidua vera at this stage of gestation with that of the Macacus. 
The human decidua vera consisted of a superficial compact and of a deeper spongy layer 
(figs. 3, 4). The compact layer was composed of a laminated arrangement of irregularly 
polygonal and somewhat flattened cells with distinct nuclei. The cells were closely 
crowded together, and the protoplasm in many was elongated into angular processes. 
It is not unlikely that the stratified cells of this compact layer were derived from and 
represented in the vera, the epithelium of the non-gravid mucosa, though they widely 
differed from the ciliated and columnar cells of the unimpregnated uterus. In this 
respect the epithelial covering of the vera in the human uterus differs in a material 
manner from what I have described in the gravid Macacus, in which animal it retains 
in the lower part of the uterus its columnar and ciliated character, though in the 
region of the fundus it forms a single layer of polygonal cells arranged in a pavement- 
like manner. 
In vertical sections through this layer in the human decidua short tubes were traced 
from the orifices opening on its surface ; they passed almost vertically through its 
thickness, but I did not see them communicate with the spaces of the subjacent 
spongy layer (fig. 3). In horizontal sections through the compact layer the tubes 
were transversely divided, and they were seen to be circular or elliptical in form. 
Occasionally two tubes were close together, but more usually they were separated from 
each other by considerable intervals occupied by the proper cellular constituents of the 
compact layer. These tubes had no special epithelial lining, but their walls were 
formed by the cells of the compact layer. Notwithstanding the absence of an epi- 
thelial lining, I have no doubt that these tubes were the ducts of the utricular glands 
which had become much more dilated than in the non-gravid condition. 
Subjacent to the compact layer was the spongy layer of the mucosa, the more 
superficial part of which had the appearance of an imperfectly differentiated con- 
nective tissue, in which were numbers of elongated fusiform corpuscles, swollen out 
somewhat at the body of the cell, where a large elongated nucleus was situated. 
4 A 
MDCCCLXX VII I. 
