138 Richard M. Fraps 



consequent upon successive ovulations are designated Lj, Lg and L3 and lag 

 by liLo and liLg. The time required for the egg to traverse the oviduct is 

 practically, if not quite, equal to the interval between a given ovulation 

 and the corresponding oviposition. 



Ovulation Frequency 



In hens exhibiting the typical "one day" lapse between sequences of n 

 members, ovulation frequency (/) is defined as /=/?/(/?+ 1 ), where /7+I is 

 equal to cycle length in days. The limit approached by nj(n+ 1) is unity. The 

 equation /=/;/(«+ 1) therefore expresses, for differing values of n, the 

 frequency of ovulation relative to the limit 1. In the 3-day cycle which has 

 proved so useful in much experimental work, n = 2 and /= 2/3 or 0.67. The 

 value of/ becomes 0.75 in the 4-day cycle, 0.80 in the 5-day cycle and so con- 

 tinues to increase by constantly decreasing increments as cycle length 

 increases. Since nj{n+ I) can only approach 1 as a limit, ovulation frequency 

 in the lengthiest of cycles can never quite attain 1.5 times the value of/ in the 

 3-day cycle. In the 2-day cycle, n= 1 and njn-\- 1 =0.50; birds so ovulating on 

 alternate days are not considered here because of the difficulty in predicting 

 continuation of the cycle. It is of interest to note, however, that hens ovulating 

 at this minimal rate or frequency (for the 1-day lapse) are in fact ovulating at 

 0.5 the maximal attainable frequency. Ovulation frequency thus measures a 

 fundamental aspect of the cycle which is obscured by sequence or cycle length 

 as such. The significance of ovulation frequency in other connections will 

 become apparent later. 



Follicular Maturation and OIH Release 



It has been assumed rather generally that the pituitary gonadotropin 

 directly responsible for ovulation in the intact hen is the luteinizing hormone 

 (LH), and further, the pituitary has been supposed by this author, at least, 

 to release LH episodically, and specifically for ovulation, in greater than the 

 "basal" quantities which, together with the follicle-stimulating hormone 

 (FSH), are required for follicular growth and maintenance. Recently, how- 

 ever, Nalbandov (44) has postulated for birds the existence of a single gonado- 

 tropic complex with FSH- and LH-like properties. A similar view has been 

 advanced by van Tienhoven (65) on somewhat different grounds. 



Evidence for the view that LH is the pituitary gonadotropin immediately 

 responsible for the induction of ovulation in the intact hen has been reviewed 

 elsewhere (17). Briefly, LH preparations from sheep pituitaries were found 

 to be much more effective than were FSH preparations from the same source, 

 and the latter were effective only when administered at levels high enough to 

 carry appreciable quantities of LH (23). Fractionation of male chicken 

 pituitaries yielded an LH preparation roughly 500 times more effective than 

 was the FSH fraction (26), and again, the ovulation-inducing effect of the 



