THE ACTION OF THYROID UPON THE GROWTH OF THE 

 BODY AND ORGANS OF THE WHITE RAT. By P. T. 

 Hekhing. (From the Pliysiology Department of the University of 

 St Andrews. ) 



{Riceived for publication ^jth March 1917.) 



I. Introduction. 



Many observations are now on record of the influence thyroid-feeding 

 exerts upon the growth of the body. The earlier literature on the subject 

 is discussed by Biedl (1) and Swale Vincent (20). References to the 

 more recent literature are given in a paper by E. R. Ho skins (11). 



Comparatively few observations have been recorded of the action of 

 thyroid upon individual organs. R. G. Hoskins (12) in 1910 described 

 hypertrophy of the suprarenals in young guinea-pigs fed for fifteen days 

 on small quantities of desiccated thyroid. Bircher (2) in the same year, 

 in an experimental research upon the production of " Kropfherz," found 

 that rats, given water from certain wells alleged to produce the disease, 

 showed diffuse colloid hypertrophy of the thyroids often accompanied by 

 degenerative changes ; there was also considerable hypei'trophy of the heart. 

 He ascribed these changes to the direct action of some toxic substance, and 



