142 



Richard M. Fraps 



Rg and R;,. If the OIH release sequence were continued in correspondence 

 with the foMicular maturation sequence, OIH release should therefore be 

 expected at or about the time of Q. Failure of OIH release to take place at 

 this time, or at any time during the period of lapse, might signify lack of 

 OIH reserves in the pituitary, or failure of the pituitary to respond to usual 

 stimuli. The possibility of OIH secretion at subovulatory levels, one aspect 

 of pituitary inadequacy, may reasonably be dismissed at the outset, since 

 subovulatory levels of ovulation-inducing gonadotropin have been shown to 

 result in follicular atresia (3, 21, 22), a condition rarely seen in the regularly 

 ovulating hen. 



Table 4. Ovulations Added to Anticipated 2-member Sequences Following Successlve 

 Injections of Male Chicken Anterior Pituitary Tissue (AP) or Progesterone (Pg) 



From Neher and Fraps (45). 



Evidence to be assessed later supports the view that progesterone effects 

 ovulation in the hen by way of the central nervous system, stimuli from which 

 cause the release of OIH from the pituitary. The induction of ovulation follow- 

 ing the systemic administration of progestcione at or about the time of C^ 

 follicle maturation (Q of Fig. 2) should therefore signify pituitary competence. 

 In an attempt to ascertain the extent to which the two-member ovulation 

 sequence might be prolonged, Neher and Fraps (45) injected progesterone or 

 male chicken anterior pituitary tissue some 24-28 hr following the presumed 

 hour of terminal OIH release and repeated such injections at 24-, 26- or 

 28-hr intervals until the ovary failed to respond by ovulation. As is evident 

 from results recorded in Table 4, progesterone was about as effective as was 

 the pituitary preparation in extending the ovulation sequence, both in mean 

 number of induced ovulations per hen and in the upper limit attained in 

 some hens. Failure to induce more than about 5 successive ovulations follow- 

 ing progesterone injection was most probably caused by failure to maintain 

 the sequence of maturing follicles, not by failure of the pituitary to release 

 OIH, since the same upper limit also was encountered following injection 



