GONADS AND THE PITUITARY BODY 



ture rat used for assay; such an explanation, however, is not 

 the only one which might be given. Swezy also found that the 

 pituitary of the rat 21 days old contained more gonadotropic 

 hormone, per unit weight, than the adult pituitary (assayed 

 in hypophysectomized adult rats and immature normal rats). 

 The experiments of Clark (1935), who estimated the gonado- 

 tropic effects of the pituitary of very young male and female 

 rats, have been discussed previously. Lipschiitz (1933-34) 

 concluded that, whereas the implantation of the pituitary of 

 adult male or immature male or female rats causes the forma- 

 tion of considerable luteal tissue, the pituitary of the adult 

 female lacks this effect because it contains little or none of the 

 hormone responsible for follicle growth and/or sensitization. 

 If a follicular change is first produced, then the pituitary of 

 the adult female rat causes luteinization. 



In their first report, Smith and Engle (1927) pointed out 

 that the effects of implants were greater in rats receiving the 

 pituitary tissue after weaning (22 days old) rather than be- 

 fore. ^^ From a study of the gonadotropic effects of pituitary 

 extracts, Selye, Collip, and Thomson (1935) concluded that 

 the ovary of the immature rat is incapable of responding to 

 the gonadotropic hormone of the pituitary (they specifically 

 mentioned the follicle-stimulating hormone) until after an 

 age of about 18 days.^' If pituitary extract was administered 

 daily from an age of 12 days, neither oestrus nor significant 

 ovarian changes were observed after 8-1 1 days' treatment 

 (ages, 20-23 days) — in marked contrast to the effects pro- 

 duced when injections were begun later or prolonged a few 

 days more. The similar injection of prolan, however, pro- 

 duced oestrus and a luteinization of the theca cells. 



The pituitary of the immature or young guinea pig con- 

 so In mice 10 days old, daily implants for 5 days were required to produce pre- 

 cocious sexual maturity; in mice 17 days old initially, daily implants were needed 

 for only 2-3 days. 



5' Also see Swezy and Evans (igjO- 



[159] 



