40 LEO LOEB 
the cell proliferation is diminished. The number of mitoses is 
usually very small, or mitoses may be absent in such follicles. 
Another characteristic feature is the relative lack of degeneration 
of the granulosa in these follicles. While the ordinary large 
follicles degenerate in the large majority of cases, the granu- 
losa cells becoming karyorrhectic, as soon as the follicle attains 
a certain size; the mature follicles are very much more resist- 
ant. The changes in the granulosa cells described above and 
which lead to the transformation of an ordinary large follicle 
into a mature red-staining follicle, and simultaneously to a de- 
crease in cell proliferation of the granulosa and to a diminished 
karyorrhexis of the granulosa cells, probably produces a decrease 
in cell metabolism, and this decrease in cell metabolism stands 
perhaps in a causal relation to the decrease in cell multiplication 
and to the greater resistance of the granulosa cell. A slight de- 
gree of degeneration of the granulosa may even occur in the ma- 
ture red-staining follicles; a few of the central granulosa cells 
may degenerate; and in one case we observed even a fargoing 
degeneration of the granulosa in a mature follicle. It becomes 
therefore probable that these mature follicles also degenerate, 
if ovulation does not take place. This transformation of an 
ordinary large follicle into a mature follicle takes place only 
to a limited extent; the large majority of the follicles degenerate 
before they have reached the stage of full maturity. This holds 
good even in the case of guinea pigs before delivery, in which a 
rupture of follicles will soon take place. 
The corpora lutea of pregnancy which, at the time at which we 
examined the ovaries, were approximately fifty-six to sixty-four 
daysold and which had formed soon after copulation, show already 
some retrogressive changes in the lutein cells. A considerable 
number of the vessels entering the corpora lutea have a very thick . 
wall consisting of several rows of cells. A large number of the 
vessels, however, have merely an endothelial lining. In many of 
the vessels no lumen is visible, the circulation through the corpus 
luteum being evidently not very active; some of the capillary 
vessels have, however, a widely open lumen. The quantity of 
the connective tissue in the centre of the corpus luteum is small, 
