EFFECTS OF THIRST — ALBINO RATS 423 



tion, and the smaller weight of the thymus in the test rats may 

 be partly due to their greater age. The weight of the thymus in 

 the test rats is far below the normal for the corresponding age, 

 however. 



In a dog on dry diet, Falck and Scheffer ('54) observed an 

 apparent loss of 63.1 per cent (body weight, -20.7 per cent). 

 Hammar ('06) has shown the general occurrence of hunger invo- 

 lution of the thymus during inanition, which has been thoroughly 

 investigated in the rabbit by Jonson ('09). McCarrison ('19) has 

 likewise noted a very great atrophy of the thymus in pigeons and 

 monkeys on vitamine-deficient diets. 



Suprarenal glands 



Since the suprarenal glands normally show a sexual difference 

 in weight from the age of about six weeks, the sexes must be con- 

 sidered separately. In the following discussion, the data concern 

 only the males. 



In the acute-thirst series the suprarenal glands show a loss of 

 21.3 per cent in average weight (table 2), while in the chronic- 

 thirst series there is an apparent loss of 27.1 per cent. In the 

 latter case, the initial body weight of the (three) male controls is 

 about 3 per cent greater than that of the test rats, so there is 

 definite loss in the weight of the suprarenals during the thirst 

 experiments. In the rat (Si. 2) after total inanition (table 1), 

 the apparent decrease in weight of the suprarenals amounts to 

 16.6 per cent. 



No data were found in the literature concerning the weight 

 of the suprarenal glands during thirst. During inanition of al- 

 bino rats with water, Jackson ('15) found in the acute-inanition 

 series an apparent increase of 1.5 per cent in weight and in the 

 chronic-inanition series a decrease of 8.9 per cent (loss in body 

 weight, 33.9 and 36.1 per cent, respectively). It therefore ap- 

 pears that during inanition with water the suprarenal glands are 

 more resistant to changes in weight than they are during thirst 

 and total inanition. In pigeons, guinea-pigs, and rabbits on 

 vitamine-deficient diets, McCarrison ('19) finds a definite increase 



