INOS 31 UTERUS AND EMBRYO. 425 
certain number of nuclei, some of which belong to leucocytes, 
others to blood capillaries, and still others, which I am uncer- 
tain about, which are few in number, and possibly belong to 
connective tissue corpuscles. The cavernous layer resembles 
now, in contrast to the first month, the upper layer of the de- 
cidua in histological constitution, but the decidual cells are 
smaller and at little wider intervals from one another; the cav- 
ernous layer is especially characterized by the slit-like spaces in 
it; some of these spaces, as indicated by the drawing, Cut 33, 
are undoubtedly blood-vessels or sinuses, but still others contain 
no blood, or at most three or four isolated corpuscles, although 
close to them are capillaries gorged with blood; once in a while 
a few epithelioid cells can be seen adhering to the walls of the 
spaces. These spaces can hardly be assigned to the vascular 
system ; they have been held by Kundrat and Engelmann, 180, 
and various subsequent writers, to be the gland cavities; we 
have not sufficient observations to establish the actual meta- 
morphosis of the areole of the one month’s uterus into the 
slits, 27, of Cuts 33 and 35, D’, but there is no ground to ques- 
tion the occurrence of the change, which appears to be a neces- 
sary consequence of the stretching of the decidua due to the 
expansion of the uterus during pregnancy. 
A complete section through the placenta zz sz¢z and uterus is 
represented in Cut 35, which has already appeared in my arti- 
cle, “ Placenta” (Buck’s Handbook, V., 696), and been sufficiently 
described. The chorion is separated by a dense forest of villi 
from the decidua, 1; the ends of some of the villi touch and 
are imbedded in the decidual tissue; these imbedded ends are 
without epithelium, but their connective tissue is immediately 
surrounded by hyaline substance. The decidua is_ plainly 
divided into two strata—cf. zxfra. The section passes through 
a wide tube, Ve, which opens directly into the interior of the 
placenta and contains blood; in my article, Zc., this opening is 
referred to as that of a vein, the identification being in accord- 
ance with my understanding of the descriptions of Waldeyer,! 
149. Professor Langhans has since informed me, that accord- 
ing to his own observations the opening of the arteries are char- 
acterized by the absence of villi projecting into their openings. 
1 T am under much obligation to Professor Waldeyer for an opportunity to examine 
some of the injected specimens upon which his very important researches were con- 
ducted. 
