452 HAYATO ARAI 
compared the results obtained by the three different methods in 
table 18. 
It is at once clear from table 18 that when body length is taken 
as a criterion, the range at which period the corpora lutea first 
appear is least, namely, the age of sixty-two to sixty-five days. 
Corpora lutea in pregnant and non-pregnant rats 
In regard to the corpora lutea there are numerous observa- 
tions, especially on their origin. Von Baer (’27) considers that 
the corpora lutea consist entirely of connective tissue, and in 
their formation the follicular epithelium has no share. On the 
TABLE 18 
Conditions determining the appearance of the first corpora lutea 
, 
THE TIME OF FIRST 
THE METHOD OF COMPARISON APPEARANCE OF CORPORA 
LUTEA 
THE AGE IN DAYS FROM 
DONALDSON’S TABLE (’15) 
BHD anv ale ds goss. ticiegedeeateiars slndonane 62 to 110 days 60 to 70 
Byabodvawelclitacc:-aemereere rer 78.5 to 100.0 grams 61 to 71 
Bysbodvyalengtiiw separ ese 148 to 150 mm. 62 to 65 
other hand, Bischoff (42) concluded that the luteal cells were 
formed by the hypertrophy of the epithelial cells of the undis- 
charged Graafian follicles. Ever since these statements were 
made by Von Baer and by Bischoff they have been the subject 
of discussion. 
Marshall (’10) stated that if the discharged ovum fails to be- 
come fertilized, the corpus luteum goes on growing for a short 
time and then degenerates. In the smaller animals it disappears 
after a comparatively short time. If, on the other hand, concep- 
tion follows ovulation, the corpus luteum continues to increase 
in size until almost the middle of pregnancy. 
Loeb (711) also found in guinea-pigs that the corpora lutea 
which are formed without pregnancy are much smaller, and 
shrank more rapidly than those the formation of which was fol- 
lowed by pregnancy. 
