BULLETIN OF THE 
IV. Degenerative Changes. 
Plate II. Figs. 14, 24-26 ; Plate III. Figs. 28, 34. 
The striking difference in the appearance of cells and nuclei, and 
the different manner of division of the nuclei, exhibited by serosze of 
different ages, have frequently been referred to. Such changes, in 
part at least, I believe to be due to degeneration of the membranes, 
which, with the exception of the ovarian capsule, are temporary struc- 
tures, soon to be cast off by the embryo. Hence it is not surprising to 
find them undergoing degeneration in toto, The degenerative changes 
are about equally well marked in all three membranes; but on account 
of the great size of cells and nuclei, the changes are most conspicuous in 
the serosa. If the membrane comes from a young embryo, the walls 
of the cells are unstainable, and therefore often difficult to make out. 
The nuclei have a vesicular appearance, with smooth, rounded contour, 
abundant karyoplasm, and scanty chromatic substance. For this reason 
the nuclei seldom stand out clearly from the cytoplasm in a stained 
preparation, often being no darker than the rest of the cell. 
Serose from somewhat older embryos, while giving no sure signs of 
degeneration, have nuclei slightly different from those of the youngest 
membranes. The amount of chromatic substance appears to be larger. 
It is gathered into denser and more deeply staining masses, and the 
nucleoli become larger and more stainable (compare Figures 4 and 5, the 
former from an older membrane than the latter). Many nuclei at this 
stage become irregular in outline, and are more or less shrunken in 
appearance, changes which prepare the way for complete degeneration, 
found in membranes from the oldest embryos. The nucleus here 
becomes shrunken into a formless mass, which stains deeply and uni- 
formly. This condition seems to be due almost wholly to loss of the 
karyoplasm, for the nuclear membrane is seen to be drawn closely 
over the much condensed chromatic substance. The uniformly staining 
effect, however, is generally believed to be produced by the solution of 
a part of the chromatin in the karyoplasm ; this is best seen in nuclei 
that have not completely degenerated, where the deeply stainable solid 
chromatin is immersed in the less stainable matrix. Not all the nuclei 
in a membrane are affected to the same degree by the degenerative 
change. This is shown in Figure 14, where the nuclei of cell a, and that 
of the cell farthest to the left, are more affected than any others. But 
in the oldest membranes almost every nucleus has undergone extreme 
degeneration. 
