INANITION OF THYROID IX HATS 333 



vious observers and my own, while differing- in various minor 

 details, agree in the main. The epithelium of the thyroid follicles 

 apparently imdergoes at first a simple atrophy, which affects 

 the cytoplasm more than the nucleus. The cells thus become 

 reduced in height, with relatively large nuclei. In advanced 

 stages of inanition, degenerative phenomena (found also to a 

 limited extent even in the normal gland) become increasingly 

 evident. The follicular cells may remain in situ, but usually 

 are desquamated, replacing the colloid (which otherwise remains 

 nearly normal). The cytoplasm, typically \'acuolated in the 

 earlier stages, may become collapsed, deeply-staining and more 

 or less homogeneous ('colloid' type) in appearance, or may dis- 

 integrate, forming an irregular granular mass. The nucleus usu- 

 ally becomes hyperchromatic, undergoing successive stages of 

 karyopycnosis, ending in extreme cases in karyorrhexis. Some- 

 times, however, it becomes hypochromatic, and undergoes kary- 

 olytic changes. 



It is somewhat remarkable that these characteristic changes 

 during inanition, — cell-atrophy with characteristic, more or less 

 extensive nuclear and cytoplasmic degeneration, — are likewise 

 found to a greater or less extent associated with a wdde range of 

 other conditions. In the foregoing pages, changes in thyroid 

 structure somewhat similar to those associated with the various 

 degrees of inanition have been mentioned in connection with 

 the following: 



1. Spontaneous (?) degeneration (in normal animals without 

 apparent cause). 



2. Age changes (tendency of cells to become flattened witli 

 age; senile atrophic changes). 



3. Functional changes (varied changes due to functional ac- 

 tivity; atrophy in the exhaustion following hyperactivity). 



4. Changes due to effects of diet (meat and other special diets; 

 administration of iodine). 



5. Toxic effects (changes produced l)y injection of vai-ious 

 toxic substances, proteid extracts, etc.). 



6. Circulatory disturbances (stasis produced l)y ligation of ves- 

 sels, etc.). 



