102 HELEN DEAN KING AND HENRY H. DONALDSON 



G! the weight is already reduced below the reference-table 

 value, and the reduction, with a slight intensification at G 6 

 and G 7 , continues to GI O . This weight change is certainly an 

 effect of captivity in the broad sense, but is most probably 

 due to a special condition represented by the food, and not 

 to the more general conditions surrounding the captive ani- 

 mal. In this sense the response of the thyroid seems a bit 

 peculiar and different from those made by the other organs. 

 At G 10 the thyroid in the captive Grays has weights close to 

 those now current in this laboratory for the Albino. Struc- 

 tural defects in the thyroid and in the parathyroid were also 

 noted (table 21). 



Suprarenal weights. Already at GX the weight of the supra- 

 renals is low. Then follows a recovery in weight which is 

 interrupted by a retardation of growth at G 6 , G 7 , and G 8 , to 

 be once more followed by a recovery that reaches about the 

 initial values. Thus, there is no progressive change in weight. 

 As compared with the wild strain, the captive Grays have 

 distinctly smaller suprarenals in both sexes, thus approach- 

 ing the relations in the Albino, but the weight relations ac- 

 cording to sex are shifted away from those in the Albino, 

 since the weights according to sex come nearer together. The 

 suprarenals are conspicuous, however, in the fullness of their 

 response to unfavorable conditions. They apparently act 

 as a sort of physiological barometer, registering directly the 

 pressure of unfavorable conditions by a retardation in their 

 growth. 



This completes the examination of the weight changes in 

 the four organs studied from G! to G 10 . There remain the 

 gonads and the parts of the skeleton (series 2) for which 

 data are available only from G 4 to GI O . Obviously, in these 

 cases nothing can be said about the initial drop in weight at 

 G!, and it is possible to compare only the G 4 with the final 

 values and to record any indication of the effect of unfavor- 

 able conditions. 



Gonads: weight. The graphs in chart 21 show that in the 

 testes the G 4 and final weights are similar. There is no 



