No. 3.] UTERUS AND EMBRYO. 403 
without any cell boundaries. In the chorion frondosum at four 
months and after I find spots where this structure still prevails, 
either with or without an underlying cellular layer; in other 
spots the layer is thickened and contains an increased number 
of nuclei, which are sometimes crowded in a bunch; elsewhere 
the layer is thinned out and has no nuclei; in still other spots 
the thickening has gone on much further, and usually, but not 
always, where the outer layer is much thickened the cellular 
layer under it is also thickened; whérever it is thickened, and 
occasionally where it is thin, the outer layer of the ectoderm 
shows a marked tendency to degenerate into canalized fibrine, 
Cut 20, fo, and Cut 22, fd. It is not difficult to assure one’s 
self that the fibrine arises by direct metamorphosis of the ecto- 
derm. I now think that its formation begins in the outer layer 
and thence spreads into the cellular layer; for, in fact, when 
both layers are distinguishable, as in Cut 22, the fibrine layer, 
fo, is always external, and the external layer of nucleated proto- 
plasm has either totally disappeared or is represented by mere 
remnants, as in Cut 22, ef. The fibrine layer consists of a 
hyaline, very refringent substance permeated by numerous 
channels, Cut 22, 76; the substance has a violent affinity for 
carmine and hzmatoxyline, and is always the most deeply 
colored part of a stained section; the channels tend to run 
more or less parallel to the surface of the chorion and are con- 
nected by numerous cross-channels ; some of the channels con- 
tain cells or nuclei. This complex system of canals is by no 
means of uniform appearance in all parts of the placenta, both 
the spaces and dissepiments varying in size and shape. The 
fibrine often sends, as shown in Cut 22, long outshoots into the 
cellular layers upon which it seems to encroach. The frequency 
of these images in my preparations led me to the opinion? that 
the fibrine arises from the cellular layer only, and I concluded 
that the ectoderm was first transformed into the so-called cel- 
lular layer, which was then transformed into fibrine. It still 
appears to me that much of the degeneration goes by these 
stages; but, on the other hand, it seems clear that the degenera- 
tion begins, as above stated, in the outer layer. Another appear- 
ance is presented by the ectoderm where it is thickened and 
wholly transformed into the cellular layer. In brief: the ecto- 
1 Anatom. Anzeiger, ii. 23. 
