348 CM. JACKSON 



SUMMARY 



The more important results of the present investigation may 

 be summarized as follows. 



In young rats held at maintenance for several weeks (and 

 hence in a condition of chronic inanition), the histological changes 

 in the thyroid are varied. The follicular epithelium is atrophied, 

 with reduction in height. The nuclei are rarely hypochromatic 

 (various stage of karyolysis), but hyperchromatosis is more 

 typical, the nuclei usually presenting some stage of pycnosis. 

 In the earlier stages the nucleus may be nearly normal in size 

 and structure, excepting a pale, homogeneous coloration of the 

 nuclear background. In more advanced stages, the nucleus di- 

 minishes in size, with deepened coloration, forming a dense, 

 deeply-staining, homogeneous mass (typical pycnosis). In ex- 

 treme cases the nucleus becomes fragmented (karyorrhexis) . 

 Neither mitosis nor amitosis is found. 



The cytoplasm is usually reduced in amount considerably 

 more than the nucleus. The cytoplasm may show no marked 

 change in structure (simple atrophy), but usually becomes rare- 

 fied, with a marked vacuohzation ('hydropic degeneration') and 

 loss of the normal granulation. This is especially marked in 

 the few cells where the cytoplasm has lost but little in volume. 

 In some cases the cytoplasm may become homogeneous ('col- 

 loid' type) and in advanced stages may disintegrate, forming 

 irregular, deeply-staining (eosinophile) masses of varied appear- 

 ance. 



The intrafollicular colloid may show no abnormal changes. 

 Advanced stages of degeneration in the follicular epithelium, 

 however, are accompanied by dissolution and disintegration of 

 the colloid. The colloid is often replaced by desquamated epi- 

 thelial cells in various stages of degeneration, and the entire 

 follicle may collapse into an irregular mass. 



The interfoUicular connective tissue (stroma) usually shows 

 no very marked change in structure, but is often increased in 

 volume by an infiltration of ground substance, giving a some- 

 what edemic appearance. On this account, the whole thyroid 



