168 John Hammond, Jr. 



midcycle ovulalion did not affect Ihc length of cycle in sheep or cattle (44). 

 It is thus unlikely that ova so shed could reach implantation and maintain 

 a corpus luteum of pregnancy. The treated animals rarely come on heat; 

 sometimes they show signs of heat but refuse to accept the male. After 

 insemination the ova are usually not fertilized (54, 71, 78), possibly because 

 the sperm are not capacitated (13); furthermore, insemination through the 

 cervix uniformly caused pyometra (78). Poor recovery of the ova shed, once 

 suspected to be due to failure to leave the follicle, is probably due to disturbed 

 ovum transport. Rapid tubal transport under the influence of the corpus 

 luteum (62, 71) would cause the ova to reach the uterus before they were 

 likely to be able to survive in the uterine secretions (12). 



Pregnant animals have been treated rarely, and usually inadvertently. 

 Ovulation has occurred after FSH as a single dose (sheep, 44) or repeated 

 doses (cow, 9), after PU following PMS (cow, 43), and after PU alone 

 (sheep, 62). But it does not seem to be induced easily by a single dose of 

 PMS (cow, 43; sheep, 62). 



During the luteal phase of the cycle, Casida et al. (9) found that repeated 

 subcutaneous pituitary injections caused follicle growth, but did not 

 uniformly produce ovulation. However, similar treatment (or with FSH) 

 when followed by an intravenous injection consistently induced multiple 

 ovulation. Multiple ovulation in sheep has been brought about in the same 

 way (54). Repeated injections of FSH, followed by PU or LH, have also 

 been used to induce multiple ovulation in cattle (78). 



After a single dose of FSH to sheep in the luteal phase, ovulation or 

 luteinized follicles were sometimes observed (44), but not after PMS. In 

 cattle Folley and Malpress (31) noted what they called "shock" ovulations 

 of one or two follicles which sometimes occurred within 48 hr of a single 

 dose of FSH but not of PMS. 



In the presence of an active corpus luteum, ovulation in cows rarely 

 occurred after PMS (71); it happened more often with a high dose, and more 

 readily after FSH (43). Multiple ovulation was, however, readily induced 

 when PMS was followed by PU (7, 71). 



Rowson (71) drew attention to quantitative and qualitative differences in 

 the response of cows to crude and purified PMS. Doses assayed as equipotent 

 in the rat were not so in cows. The purified material produced less follicle 

 growth and furthermore a smaller proportion of the large follicles ovulated 

 when PU was administered. While this might be due to loss of synergistic 

 LH activity during purification it is conceivable that differences in rate of 

 absorption or elimination are responsible. 



The effect of a single large dose of gonadotropin may be prolonged (31). 

 Brock and Rowson (7) found the number of follicles ovulated by PU after 

 PMS increased until the interval between the two treatments was at least 

 7 days. Abnormal, cystic looking, and partly luteinized follicles may be seen 



