THE PITUITARY BODY 



generally follows a "stimulation" of the testes or ovaries of 

 the normal rat with appropriate secondary changes in the 

 accessory sexual organs. The experiment demonstrating this 

 fact most clearly is that in which a castrated male rat and a 

 normal female rat are made parabiotic ( 9 isT)- Yatsu (1921) 

 correctly inferred that the changes in the female genital tract 

 were due to the transfer of hormone or hormones from the 

 castrated male; only more recently, however, has it been pos- 

 sible to demonstrate that the pars glandularis of the pituitary 

 of the castrated male is the probable source of the hormone. 

 As will be shown later, the internal secretions of the testis and 

 the ovary (at least "oestrin") lessen the secretion (or storage) 

 of gonadotropic hormone by the pituitary. If this inhibiting 

 influence is removed, as by gonadectomy, an excess of gonad- 

 otropic hormone is produced by the gonadectomized animal 

 (which presumably also no longer utilizes the hormone). It is 

 then carried to the parabiont with intact gonads and adds its 

 effect to the hormone secreted by the normal animal's pitui- 

 tary so that an unusual development of the ovary (or testis) 

 follows. 



Ordinarily the internal secretion of the ovaries or testes, 

 liberated in increased amounts because of the gonad-stimula- 

 tion (as in the experiments 9 ^ and cf ^) affects the acces- 

 sory sexual organs only of the normal rat. This may be due 

 to such factors as inadequate supply for both animals, too 

 slow a transfer of the hormone, etc. According to M^ller- 

 Christensen (1933), however, oestrus is more frequently ob- 

 served in the spayed rat of the experiment 9 ? if the rat with 

 intact ovaries has been hypophysectomized before parabiotic 

 union. 



According to Witschi and Levine (1934), the establishment 

 of marked follicular growth and oestrus in the experiment 

 9 -^ may be delayed as long as several months. They stated 

 that during the first few weeks after such a parabiotic union, 

 anoestrus and the formation of corpora lutea in unusual num- 



[148] 



