68 



Scientific Proceedings (56). 



and in every case of thyroidectomy postmortem examination 

 showed that the thyroid had been completely removed. The 

 body weight of each animal was corrected by deducting the weight 

 of contents of stomach, intestines, and bladder. The pituitary 

 was carefully dissected out and weighed to the tenth of a milligram 

 and the weight of each pituitary was then calculated in milligrams 

 per kilo of corrected body weight. 



The average weight of the pituitary, of the animals under the 

 above-described conditions, in milligrams per kilo of corrected 

 body weight may best be seen in the following table. The figures 

 in parenthesis indicate the number of animals used in each case. 



Thyroidectomized. 

 Fed (4). Not fed (2). 



14.72 14.80 



Thyroidectomized. 

 Fed (3). Not fed (2). 



13.26 23.43 



Females. 



Males. 



Controls. 

 Fed (4). Not fed (4). 



14.56 13.90 



Controls. 

 Fed (4). Not fed (4). 



12.81 10.79 



In the literature dealing with this subject it is generally agreed 

 that removal of the thyroid is followed by an increase in the weight 

 of the pituitary, but whether this increase is due to absence of the 

 internal secretion of the thyroid or to some other cause has not 

 been determined. If feeding thyroid to rabbits which have been 

 thyroidectomized prevents the increase in size of the pituitary 

 this would point to the conclusion that the determining factor is 

 to be found in the internal secretion. Such seems to be the case 

 in the male thyroidectomized group where no increase in pituitary 

 weight is evident while thyroid substance is being supplied, but 

 when not fed the weight of the gland is almost double the normal. 

 The female thyroidectomized group however does not show this 

 but here it will be observed that apparently the pituitary did 

 not increase in size after removal of the thyroid where no desiccated 

 gland had been fed and this might be explained by supposing 

 that in these individual animals the glands happened to be un- 

 usually small to begin with. 



No effect on the pituitary weight was observed from feeding 

 desiccated thyroid to normal rabbits. 



The substance fed was proved to be active by administering it 



