THE GONADOTROPIC HORMONES 



he concluded that the action of folhcle-stimulating hormone 

 (of the pig's pituitary) is inhibited if, prior to injection, it has 

 been mixed with luteinizing hormone, lactogenic hormone, 

 or an extract of pregnancy-urine. 



Compensatory hypertrophy of the testis as well as several 

 other phases of the pituitary-gonad interrelationship was 

 studied in Leghorn cockerels by Belsky (1936). The author 

 concluded that the compensatory hypertrophy in young birds 

 is associated with pituitary hypertrophy. Under other condi- 

 tions hypertrophy of the pituitary is associated with an ab- 

 sence or diminution of gonad function (castration or times 

 of seasonal rest of the gonads). 



Brown Leghorn hens were hypophysectomized by Hill and 

 Parkes (1935). The expected reversion of the feathers to the 

 male (asexual) type was observed only in the neck hackles. 

 Plumage changes characteristic of thyroidectomy appeared 

 in the hypophysectomized cock. These changes as well as 

 atrophy of the testis and comb could be lessened only for a 

 few days by the injection of beef anterior pituitary extract. 

 The administration of testicular hormone, but not of oestrone, 

 caused growth of the atrophied comb. 



Witschi and Keck (1935) investigated the action of extract 

 of the pituitary of the horse and ox on the gonads of the 

 English sparrow. Preliminary observations indicated that 

 great seasonal variations occur in both sexes — marked growth 

 of the gonads occurring in spring and early summer and rapid 

 involution taking place in July and August.^ Secondary sex- 

 ual characters such as the color, shape, and texture of the 

 bill underwent corresponding alterations. The daily adminis- 

 tration of pituitary gonadotropic hormone (e.g., 2 rat-units 

 for 16-33 days) could cause a sixty-fold increase in the size 

 of the testis or ovary of birds with resting gonads. The antic- 

 ipated alterations in secondary sexual characters, such as 



^ During involution the testis might regress to one-thousandth its previous size; 

 the ovary might atrophy to the size of that of an immature bird 2-3 months old. 



[55] 



