324 C. M. JACKSON 



the interstitial substance is probably sutficient in most cases to 

 offset the decrease in volume of parenchyma, so that if the col- 

 loid remains approximately normal in amount, the stationary 

 absolute weight of the adult thyroid gland during inanition is 

 explained. The greater tendency to loss in weight of the thyroid 

 during chronic inanition and in younger rats is probably due to 

 greater atroi:)hy of the i:)arenchyma, and in some cases to loss of 

 colloid. 



«WW- 





Fig. 10 From a pliotijgrapli of a i)ortiou of tlu> thyroid gland of a normal 

 adult rat (No. S 14 x, gross body-weight 252 grams), moderately magnified to 

 show typical 'spontaneous' degeneration of the follicles. Nuclei in various stages 

 of pycnosis. Tendency to desquamation of epithelium with obliteration of the 

 follicular cavity. (X 350.) 



(L Discussiori and conclusions 



The question of the extent and significance of the normal vari- 

 ation in tlie thyroid, with especial reference to the so-called de- 

 generative changes, will be considered first, followed by a dis- 

 cussion of the specific changes produced by inanition. 



The extreme variability in the form and structure of the fol- 

 licular epithelium was observed by many of the earlier investi- 

 gators. These variations were usually ascribed to age differ- 

 ences or to functional changes. The frequent presence of cells 



