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RlCllAKl) M. FRAPS 



indifferent to the ovulatory stimulus, yet the same follicle responds by 

 ovulation to the succeeding 01 H release, Ro of the sequence. 



In our early experiments on the induction of ovulation, injections were 

 timed for effect on follicles subsequent to the lirst of a sequence (C^ follicles), 

 since in these the hour of normally expected ovulation could be predicted 

 accurately. When subsequently the response of the Ci follicle was investigated, 

 it was found — somewhat surprisingly at the time — that its ovulation could 

 be induced at considerably greater intervals before normally expected ovula- 

 tion than was possible with other follicles of the sequence (14, 21, 22). Or, 

 following injection of appropriate gonadotropins at equal but considerable 

 intervals before the hour of normally expected ovulation of C^ and Q 

 follicles, the C^ follicle was found to be much the more sensitive, as was 

 confirmed by Bastian and Zarrow (3). A similar differential in ovulatory 

 response of Ci and Q follicles to progesterone was described by Fraps 

 and Dury (23, 24). 



Table 3. Approximate Quantities (mg/hen) of Male Chicken Anterior Pituitary 

 Powder Inducing Ovulation of Cj and C^ Follicles in about 50% of Intravenously 

 Injected Hens at Indicated Hours Following Preceding Ovulation (/7 = 2 for 



ALL hens) 



When the earliest hour at which notable sensitivity of the Cj follicle could 

 be demonstrated experimentally was considered with reference to time of 

 preceding ovulation rather than to time of next expected ovulation, its high 

 ovulability was seen to be attained at about the same interval following the 

 preceding ovulation as did subsequent follicles of the sequence. This supposi- 

 tion was tested by ascertaining the quantity of dried male chicken anterior 

 pituitary powder required to force ovulation of Cj and Cg follicles of 

 2-member cycles in about 50% of hens injected at increasing intervals follow- 

 ing the preceding ovulation. [Unpublished experiments of Fraps, Rothchild and 

 Nehcr; summarized by Fraps (17).] The "best estimate" of responses follow- 

 ing closely upon preceding ovulation leaves much to be desired, but ovulability 

 of Ci and Ca follicles clearly increases with increasing time from preceding 

 ovulation (Table 3). The similar and high sensitivities at 19 hr seem of particu- 

 lar significance, for following injections at this interval after the preceding 



