THE PITUITARY BODY 



important gonadotropic hormones are the folHcle-stimulating 

 and luteinizing hormones. Fevold and Hisaw and their co- 

 workers have emphasized that the production of ovulation 

 requires both hormones. Other experiments indicate that the 

 secretion of luteinizing hormone in appropriate amount and 

 at the proper time following follicle growth also is essential 

 for normal oestrus, so that without this hormone, ovulation, 

 mating, corpus luteum formation and maintenance^ — and 

 hence pregnancy — cannot occur (Casida, 1934; Witschi and 

 Pfeiffer, 1935; Dempsey, Hertz, and Young, 1936). Casida 

 suggested that atretic corpora lutea are due to the adminis- 

 tration of an excessive amount of luteinizing hormone. Rid- 

 dle and others (1936), unable to demonstrate augmentation of 

 the ovulation-producing effect of follicle-stimulating hormone 

 by luteinizing hormone, concluded that the latter is not neces- 

 sary for ovulation. Inasmuch as their experiments were not 

 performed in hypophysectomized rabbits, this conclusion 

 does not appear to be warranted. The difficulty of the experi- 

 mental production of ovulation in the oestrous cat was em- 

 phasized by Foster and Hisaw (1935), who concluded that at 

 least some luteinizing hormone — even in minute amount rela- 

 tive to the dose of follicle-stimulating hormone — must be 

 administered to cause ovulation. The authors also studied 

 the duration of pseudopregnancy which persisted 40-44 days. 

 In the cats of van Dyke and Li (1938) pseudopregnancy per- 

 sisted only about 20 days; however, they produced a much 

 smaller number of corpora lutea than did Foster and Hisaw. 

 Van Dyke and Li used prolan also. Experiments in the im- 

 mature monkey have been described by Hisaw (1935). 



Pfeiffer (1937) believed that the male rat pituitary secretes 

 or is able to release much less luteinizing hormone than the 

 female. According to Bunde and Creep (1936), luteinizing 

 hormone or some substance associated with it can cause the 

 rapid regression of corpora lutea in hypophysectomized young 

 adult rats. The earlier experiments of Smith demonstrated 

 how remarkably long the corpora lutea persist after hypophy- 



[72] 



