INANITIOX OF THYROID IN RATS 329 



111 a recent coniinunication in repl>' to a letter of inquiry by 

 tlie author, Dr. Marine states that he has frequently observed 

 the so-called degenerative changes in the thyroid of the rat and 

 other animals, and comments as follows: 



I personally consider this change as a kind of autolysis. Autolj^sis 

 in the thyroid is perhaps more easil^^ recognized than in any other or- 

 gan of the body because of its simple architecture. The change of 

 which you speak consists of a desquamation of the alveolar cells and 

 a Ijreaking up of the cell membrane, giving a ragged appearance to the 

 free border of the cells. This is always more marked in the slightly 

 hyperplastic stages. Much has been mad(^ of this by various experi- 

 menters in an attempt to bring it into relation with th(> specific experi- 

 ments that they were studying. It is of too general occurrence to 

 have so varied a significance. The rat and the chick we have found 

 to show these changes most frequently. One sees it in all chicks or 

 rats that are autopsied some hours after death and even in rats sacri- 

 ficed and autopsied at once, as all ours have been just for the purpose 

 of eliminating this autolysis. I also think that formalin fixation is 

 favorable for its developnu^it, as one rarely sees it in strictly fresh 

 thyroids that have been fixed with metallic salts. In hunum thyroid 

 patholog}', as you are aware, this change has l^een described in almost 

 every paper and in connection with the Basedow syndrome. Most 

 writers who have studied the human thyroid have attempted to ascribe 

 some peculiar toxic value to it. This is wrong. It is present in the 



cretin thyroid oi* in any active hyperplastic thyroid as well 



In conclusion, therefore, I believe that this change is quite common in 

 rats and fowl thyroids generally, and is of frequent occurrence in all 

 tliyroids unless the s])ecial precaution is taken of ol)taining the tissues 

 strictly fresh and fixing them in solutions other than formalin. I do 

 not think it is any more connnon in starvation ex])(M'iments than in 

 other groups. 



Itanight also be added that glands which have not been placed 

 promptly in the fixative, and in which the process of post mortem 

 autolysis has begun, sometimes show considerable differences in 

 appearance at different depths from the surface. The fixation 

 is better in the superficial layers than in the deeper strata which 

 require a longer time for penetration. 



In order to compare the structure of the thyroid gland, and 

 especially the occurrence of degeneration, in the rats used b^^ 

 me with those elsewhere, I have obtained material from various 

 localities. Professor Addison, of the University of Pennsylvania, 

 kindly furnished mounted spechnens of the thyroid from 3 nor- 



