ADRENALECTOMY 147 



Season. The survival of adrenalectomized animals is depend- 

 ent upon their state of activity at the time of operation. 

 Hibernating animals survive for extended periods while the 

 same animals during their summer activity survive adrenalec- 

 tomy for a much shorter time. 86 



Pregnancy. H. A. Stewart 593 first noted the prolongation 

 of the survival of adrenalectomized pregnant cats as compared 

 to non-gravid females. G. N. Stewart and Rogoff 529 found a 

 mean survival period of 7 days for male and 6^ days for non- 

 pregnant female dogs as compared to 22 days for pregnant 

 animals. Similarly in rats, Firor and the author 198 observed a 

 prolongation of life in pregnant as compared to non-pregnant 

 animals. Other authors 125 have failed to note any prolongation 

 in the survival of pregnant animals. Their results might be 

 explained by the fact that during pregnancy (particularly when 

 advanced) the glands are less easily accessible for operative 

 removal. Since pregnant animals are more susceptible to 

 injury by any operative manhandling, the survival after 

 adrenalectomy may be unaffected or even shortened (as com- 

 pared to non-pregnant animals) unless the operation is carried 

 out with great technical skill and celerity. 



The prolonged survival of pregnant animals may be ex- 

 plained by assuming that the cortical hormone produced by the 

 embryo is transported through the placenta to the maternal 

 tissues. 



Estrus. As demonstrated by Rogoff and Stewart, 533 dogs 

 adrenalectomized during or shortly after estrus survive for a 

 much longer period than animals in diestrus. The explanation 

 for this phenomenon probably lies in the fact that the increased 

 body activity during natural estrus stimulates the adrenals to 

 the production of a greater store of the hormone in the body 

 than is normally present. There is no reason to believe, as has 

 been suggested, that the corpus luteum (whose cells resemble 

 superficially those of the adrenal cortex) takes over the func- 



