GROWTH AFFECTED BY FEEDING DUCTLESS GLANDS 339 



The organs of the rats which received very httle thyroid were 

 not much affected in weight, but in the rats which received larger 

 doses (see tables 6 to 10) several of the organs are e\ndently 

 h>T3ertrophied. This cannot be interpreted as merely a relative 

 gain, due to loss of body-fat, for the body weight, as above stated, 

 has apparently suffered no loss in the thyroid-fed rats, but pos- 

 sibly a sHght gain instead. The organs which show a consider- 

 able increase in weight are the heart, liver, spleen, suprarenals 

 and kidneys. 



Other organs in which the results are more doubtful, but which 

 seem to be increased in weight to a greater or lesser extent are 

 the hypophysis (male), and alimentary canal, and possibly 

 the skeleton, testes, and epididymi. The increase of this group 

 of organs is uncertain, and in some cases probably due -to 

 chance variations. 



These results are in general agreement with those of Iscovesco 

 ('13) who (by thyroid extract injections) found hypertrophy 

 of the heart, thyroid gland, suprarenals, kidneys (male), testes, 

 ovaries and uterus. He reports an increase in the weight of 

 these organs of nearly 100 per cent, but no increase in the weight 

 of the liver or female kidneys. My results confirm also the 

 hypertrophy of the suprarenal glands found by Rudinger, Falta 

 and Eppinger ('08), and by Hoskins ('10a). They also confirm 

 to some extent the results of Bircher ('10a) (10b), who found 

 that hyperthyroidism produces enlargement of the heart and 

 thjToid gland, and acceleration of skeletal development. They 

 do not, however, agree with Utterstrom ('10), who found en- 

 largement of the thymus. 



It may be noted further that these results Hkewise agree with 

 the generally accepted doctrine that hyperthyroidism produces 

 a general acceleration of metabolism. Conditions increasing 

 metabolism would naturally throw a greater burden upon the 

 important viscera, and thus tend to produce in them a hyper- 

 trophy. Thus Hatai ('15) has shown that increased exercise 

 in albino rats tends to produce an enlargement of various organs, 

 and his results resemble closely those obtained by me with thy- 

 roid feeding. 



