The Corpus Luteum of the Guinea Pig 



75 



vesicular follicles are to be found. But as Loeb noted, a new 

 wave of follicular growth then takes place and by the 8th 

 to 10th days mature follicles are present, and in the series of 

 ovaries examined at least one of these structures was found 

 throughout pregnancy. No evidence of spontaneous ovulation 

 was obtained. 



A few initial experiments indicated that a dose of 50 i.u of 

 chorionic gonadotrophin was sufficient to induce ovulation in 

 pregnancy. A summary of the results obtained in 33 guinea 

 pigs, given in Table I, indicates that the follicles in early 



Table 1 



pregnancy (8 to 20 days) are less sensitive to the action of the 

 hormone than are those occurring in late pregnancy, when the 

 average number of follicles that rupture is nearly doubled. 



The Fate of the Ruptured Follicle 



Guinea pigs were injected with chorionic gonadotrophin on 

 the 8th, 20th and 35th days of pregnancy; they were killed 

 8, 14, 20 and 28 days later and the induced and the normal 

 corpora lutea were measured as described above. Classification 

 of the two sets of corpora lutea was based on qualitative rather 

 than quantitative differences shown. By these means the 

 induced corpora lutea at 8, 14 and 20 days of age are readily 

 distinguishable from those of pregnancy, but in some ovaries 

 the differences between the 28-day-old induced corpora lutea 



