552 
PROFESSOR W. TURNER ON THE PLACENTATION OF THE APES. 
could be seen, which in size and shape resembled those seen in a placenta in the ninth 
month. In the last month of pregnancy a definite layer of cells was seen on the 
placental surface of the chorion, not limited, as Kolliker, has stated, to the marginal 
lobes, but extending generally over its whole surface. These cells were polygonal in 
shape and in contact with each other by their edges, so that they formed a definite 
layer. Their nuclei were relatively large, the protoplasm granulated ; and in size, 
shape, and appearance they closely resembled the large cells of the compact layer of 
the decidua placentalis. In their position and general characters they were like the 
sub-chorionic cells of the Mcicacus, but instead of possessing as in that animal a 
stratified arrangement so as to form a membrane thick enough to be seen with the 
naked eye, they formed, so far as my observations have gone, apparently only a single 
layer of cells. 
There are difficulties in the way of giving a satisfactory account of the mode of 
origin of the sub-chorionic cells in the human placenta. Their position and characters 
point to one or other of three sources — modified chorionic epithelium, intra-chorionic 
cells, or from the decidua serotina. I do not think it likely that they can be modified 
chorionic epithelium, for they not only differ so much from the cells of that epithelium 
in appearance and size, but, from Langhans’s observations and my own, there is every 
reason to believe that the chorionic epithelium degenerates and disappears in the human 
placenta about the middle of pregnancy. 
Many facts and arguments are advanced by Langhans in favour of their origin in 
the human placenta, where alone he has studied them, from the vascular layer of the 
chorion, and I must refer to his memoir* for a full discussion of the subject. Here, 
however, I may state that before his memoir was published I had observed in Mcicacus 
cynomolgus, in addition to and quite distinct from the sub-chorionic cells, rows of intra- 
chorionic cells having a granulated protoplasm, such as one finds in the cells of the 
decidua, which bad obviously originated within the chorion (p. 532). These intra- 
chorionic cells, however, did not form a continuous layer, but were broken up into 
groups, separated from each other by fibrillated connective tissue, and situated near 
the amnio tic surface. 
The sub-chorionic cells in Mcicacus had a different arrangement, not only from the 
intra-chorionic cells, but from the sub-chorionic cells as described in the human 
placenta by Langhans, or as seen by myself. They were not broken up into groups 
or patches, but possessed a continuous stratified arrangement over the whole placental 
surface of the chorion, and invested the stems of the villi so that the fibrillar struc- 
ture of the chorion was excluded from forming the boundary of the intra-placental 
maternal blood spaces. The fact that between the deeper layers of these cells the 
proper tissue of the chorion seemed to penetrate, points to the origin of these deeper 
layers at least from the chorion, and to their homology with the intra-chorionic cells. 
The great resemblance between the more superficial layers of these cells and the cells 
* ‘ Arcliiv fur Anat. und Phys.,’ 1877, p. 256. 
