58 LEO LOEB 
In regard to the ordinary corpora lutea and the corpora lutea of 
pregnancy of previous generations, the same retrogressive changes 
which were described above in the ovaries of non-pregnant guinea 
pigs of this period, were found in pregnant animals. 
We see therefore that the condition of the corpora lutea indi- 
cates the condition of the follicles, and conversely the condition 
of the follicles indicates the history of the corpora lutea. At a 
certain time (approximately ten days) after the ovulation a 
certain equilibrium is reached between the growth and the degen- 
eration of the follicles. Whether a quantitatively exact equili- 
brium is reached, cannot yet be stated. In proportion to the 
length of time which elapsed since the last ovulation, the probabil- 
ity of a new spontaneous rupture, with the subsequent changes in 
the follicles, becomes greater. At this and the preceding period 
signs of degeneration are present in the ordinary corpora lutea, 
which become the more marked the older the corpus luteum; the 
number of mitoses in lutein cells decreases with advancing age; 
they may however still be present in corpora lutea immediately 
following a new ovulation; the latter however is soon followed by 
further progressing degeneration of the corpus luteum of the pre- 
ceding ovulation. If the ovulation that took place twenty to 
twenty-six days previously was accompanied by pregnancy, 
no new spontaneous rupture of follicles took place, the prolifera- 
tion of the lutein cells continued, and degenerative processes in 
the corpora lutea were retarded. 
Approximately twenty-five days after the completion of preg- 
nancy the corpora lutea of pregnancy (second generation) have 
become small vacuolar bodies with thick vessels and fibrous tissue, 
while corresponding ordinary corpora lutea have at this time 
apparently been transformed into yellow bodies. 
