Ovulation in the Domestic Fowl 141 



ovulation the C, follicle is forced to ovulate prematurely by no more 

 than about 3 hr in contrast with a prematurity of some 17 hr for the Q 

 follicle. 



In an extensive series of experiments, Bastian and Zarrow (3) determined 

 the quantities of luteinizing hormone required to induce ovulation of first 

 and subsequent follicles of the sequence at stated intervals before the hour 

 of expected normal ovulation. Their results were in important respects very 

 similar to those described above, although they appear not to have recog- 

 nized the possibility of similar courses in maturation of Cj and Q follicles 

 with reference to hour of preceding ovulation. The possibility that failure of 

 the highly ovulable Cj follicle to ovulate earlier than it actually does because 

 of "lack of release of ovulating hormone" (14) is noted, but Bastian and 

 Zarrow consider also, and with greater favor, the possibility that the observed 

 high degree of sensitivity could be the result of "a release of the ovulating 

 hormone on the night prior to ovulation", but at levels inadequate to induce 

 ovulation. If, however, the course by which the Ci follicle attains ovulability 

 is in fact substantially the same as that of Cg follicles, no special condition 

 need be postulated for this fact, nor for its continuing and perhaps even 

 slightly increasing sensitivity to OIH preparations as it approaches the hour 

 of actual ovulation. 



The foregoing observations are believed, in any event, to afford strong 

 evidence for the conclusion that the Ci follicle does in fact attain to ovulability 

 by substantially the same course, with reference to time of preceding ovula- 

 tion, as do other follicles of the sequence. In Fig. 2 the curves Mg, Mg and M/ 

 are seen thus to stand in an approximately constant relationship with ovula- 

 tions Oi, O2 and O3 respectively. But since the onset of OIH release is believed 

 to take place at a constant interval before each ovulation of the cycle, the 

 courses of increasing ovulability represented by Mg, M3 and M/ bear also an 

 approximate constancy with respect to the postulated OIH releases, Ri, Rg 

 and R3. The question might then be raised as to whether OIH, or endocrine 

 factors associated with processes of follicular rupture, initiate maturation of 

 the succeeding follicle of the cycle. This author has more or less tacitly 

 assumed that OIH is the effective agent, but little evidence bears directly on 

 the issue. If the pituitary gonadotropin secreted into the blood stream is in 

 fact a single entity, as Nalbandov (44) and van Tienhoven (65) suggest, an 

 episodic release of OIH would imply relatively high levels of FSH as well as 

 of LH activity. The initiation of follicular maturation might then be attributed 

 to such episodically recurrent periods of high FSH activity, but this must 

 remain a matter of conjecture at the moment. 



Pituitary Competence during the Period of Lapse 



In Fig, 2, the Ci' follicle is seen to have become fully ovulable at about 

 the time Q, the interval between R3 and Q being made the same as between 



