WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 



135 



TABLE 13 



The thyroid gland; average absolute weight, average percentage of net body-weight and 



range indicated 



DESCRIPTION OF RATS 



absolute weight 

 (and range): grams 



RELATIVE WEIGHT 



(AND range) : 



PER CENT 



Normal at 3 weeks (Jackson '13) 



Controls at 3 weeks 



Body-weight constant 3 weeks (age ot 3 to 6 weeks) 

 Body- weight constant 5 weeks (age ot 3 to 8 weeks) 

 Body-weight constant 7 weeks (age of 3 to 10 weeks) 

 Normal at 10 weeks (Jackson '13) 



0.0060 (0.0034-0.0104 

 0.0078 (0.0064-0.0094 

 0.0053 (0.0052-0.0056 

 0.0058 (0.0047-0 0068 

 0.0059 (0.0034-0.0087 

 0.0165 (0 0100-0.030) 



0.030 (0.018-0.041) 

 0.033 (0.022-0.042) 

 0.023 (0.022-0.024) 

 0.032 (0.026-0.038) 

 0.025 (0.016-0.036) 

 0.015 (0.008-0.022) 



of the body to 0.025 per cent. Or, in terms of absolute weight, 

 it has decreased from 0.0078 to 0.0059 grams, a decrease of 24 

 per cent. (A slight correction should be made on account of 

 difference in body-weight.) No observations were made upon 

 the thyroid gland in the experiments beginning at later ages. 



During acute inanition in adult rats, the thyroid gland appar- 

 ently loses little or no weight; while in chronic inanition with 

 an average loss in body-weight of about 36 per cent, the thyroid 

 gland loses only about 22 per cent in weight (Jackson '15). 

 There is some uncertainty as to the exact figures, however, on 

 account of variability and difficulty in dissecting out the thyroid 

 gland in an accurate manner. The same, of course, holds true 

 for the present series. 



THY^IUS 



The normal thymus (table 14) at three weeks forms 0.37 per 

 cent of the net body-weight. This decreases, in rats held at 

 constant body-weight, to 0.075 per cent at six weeks of age, to 

 0.030 (exceptional?) at eight weeks, and to 0.040 per cent at ten 

 weeks. In terms of absolute weight, the thymus has decreased 

 from 0.091 grams at three weeks to 0.017 grams (loss of 81 per 

 cent) at six weeks, and .to 0.0094 grams (loss of 90 per cent) at 

 10 weeks. No correction for the slight difference in body-weight 

 has been made in these estimates. 



Normally at ten weeks of age the weight of the thymus should 

 have increased to about 0.24 grams (0.30 grams in the controls). 



