THE GONADOTROPIC HORMONES 



will be made to recapitulate the older experiments with 

 parabiotic animals; an outline of the results of these experi- 

 ments will be found in the earlier volume. The outstanding 

 fact previously demonstrated is that, if a gonadectomized and 

 a normal animal are joined in parabiosis, an abnormal stimu- 

 lation of the gonads occurs and persists for months, because, 

 in all likelihood, abnormal amounts of pituitary gonadotropic 

 hormone are present in the blood. This is particularly true 

 of the experiment 9 s^.^^ In the experiment cf sf, the acces- 

 sory organs of the castrated male remain atrophic. However, 

 according to McCullagh and Walsh (1935), the injection of a 

 comb-growth-stimulating hormone ("androtin") prevents 

 both a gonadotropic effect in the normal male and a regres- 

 sion of the accessory organs in the castrated male.^^ De 

 Mello (1936) placed an ovarian graft in the normal male of 

 the parabiotic pair^ cT. A hypertrophy of the prostate and 

 seminal vesicles of the normal male, abnormal even for such 

 an experiment, apparently was caused by the combined ef- 

 fects of ovarian and testicular secretions. Both the graft and 

 the testes iri situ were stimulated. 



Recently additional observations have been made on the 

 results of parabiosis between hypophysectomized and normal 

 or gonadectomized rats. In experiments of the type cTh^, 



spayed female; cf refers to a normal male; isf refers to a castrated male; ^ih refers 

 to a hypophysectomized female, etc. d^htsT would refer to a parabiosis between 

 a hypophysectomized male and a castrated male. 



** In this experiment, the ovaries become cystic and remain in this condition for 

 months. Coincidently, the changes characteristic of oestrus are observed in the 

 uterus and vagina. Evans, Simpson, and Pencharz (1935) suggest that the castrated 

 male pituitary contains (secretes?) but does not release luteinizing hormone. They 

 implanted the pituitary of castrated male rats into female rats hypophysectomized 

 at an age of 26 days. Follicle-stimulation followed the smaller dose of pituitary 

 tissue, whereas corpora lutea were formed after the larger dose (4 glands of young 

 males 40 days after castration). Four glands of normal males caused only follicle- 

 stimulation in accordance with the belief of some authors that the normal male 

 pituitary "releases" only follicle-stimulating hormone. 



^' The authors stated that a specific substance in testicular extract ("inhibin") 

 prevents oestrous cycles in the female rat and causes atrophy of the male accessory 

 organs, 



[79] 



