124 A. V. Nalbandov 



the other. In the folHcle walls of chicken and frog ovaries true smooth muscle 

 cells are present. The occurrence of smooth muscle cells in these and probably 

 other species made it reasonable to think that their presumed ability to con- 

 tract may play a role in bursting ripe follicles. Many abortive attempts have 

 been made to induce ovulation by substances known to cause contraction 

 of such fibers or by the electrical stimulation of the follicle wall (3). Oxytocin, 

 injected systemically into rabbits, not only does not hasten ovulation but 

 prevents it completely (2). 



The injection of LH-containing gonadotropins may hasten ovulation by 

 several days in mares, or by several hours in chickens, pigs and cows. 

 Similarly, ovulation may be delayed by the use of such blocking agents as 

 atropine in rabbits and cows or dibenamine in chickens. Thus, the follicle 

 seems to become capable of ovulating long before it is normally called upon 

 to do so by endogenous LH. It also retains its ability to ovulate past the 

 normal time of rupture, if the release of LH is blocked or delayed by experi- 

 mental means. The follicle of the mare remains ovulable for three to seven 

 days and in the hen, under certain experimental conditions, it retains its 

 ability to ovulate for as long as three weeks after it has reached ovulatory 

 size (8). 



Considering the data briefly summarized thus far, it appears justifiable 

 to conclude that follicles reach ovulability before their "destined" time to 

 rupture and retain their ability to ovulate for a considerable time after this 

 event should have normally occurred. The follicle, not unlike a sound 

 sleeper who will be awakened by an alarm clock, is unaware of its fate but, 

 like the well-rested sleeper, it is physiologically ready and waiting passively 

 for the signal to begin the final transformations leading to its ultimate fate — 

 ovulation. For the follicle the signal is the arrival of LH. This signal is 

 comparable to the ringing of an alarm clock which, having run down, leaves 

 no memory of its sound other than the effect it produces on the suddenly 

 altered metabolism of the awakened sleeper. 



The data to be presented are concerned with the possible nature of the 

 transformations which take place in the follicle between the time it receives 

 the order to ovulate and ovulation itself. 



Before discussing further the theoretical aspects of the problem of the 

 ovulability of the follicles, data will be presented bearing on this problem in 

 laying hens. Similar work is in progress in mammals but it is not sufficiently 

 conclusive to permit discussion at this time. The experimental work to be 

 presented involves laying hens which were hypophysectomizcd after they 

 had laid the first two eggs (Q and Cg) of their clutch which in these birds 

 normally consists of four or more eggs. Since, in the hen the interval between 

 LH release and ovulation is variously estimated to be 8 to 12 hr in length, all 

 hypophysectomies were performed about 1 8 hr before the expected ovulation 

 of the C3 follicle. Thus, there was a good margin of safety to make certain 



