12 Iodine in the Thyroid Gland 



thyroid gland appeared to be directly proportional to the degree 

 of hyperplasia exhibited by the gland. In a second communica- 

 tion (3) they discussed the time of appearance of the changes in the 

 histology and physiological activity of the gland following the 

 intravenous administration of KI solution. 



Having found (4) that there was relatively little difference in 

 the ratio of the percentage of iodine in cells to the percentage of 

 iodine in whole gland in dog thyroid glands exhibiting great 

 variations in histological appearance and iodine content, I under- 

 took the present study to determine what effect acute iodization of 

 hyper plastic thyroid glands has on the ratio value. 



Methods. 



As in the work of Marine and Feiss, and Marine and Rogoff, 

 dogs with thyroid glands usually definitely hyperplastic were 

 used in all of the experiments. Light ether narcosis was always 

 employed. All solutions of KI and thyroid colloid were injected 

 into the femoral vein. Every effort was made to section the glands 

 as rapidly as possible after their removal from the animal. In 

 the making of the determinations of the ratio of the percentage 

 of iodine in dried cells to that in dried whole gland the method 

 first described by Tatum (5) was somewhat modified. To lessen 

 autolysis as much as possible the glands on removal were plunged 

 into Ringer's solution cooled to 1^C. The glands were then 

 carefully cut into blocks of a size appropriate for the floor of the 

 freezing microtome and frozen sections were made of a considerable 

 amount of tissue. The blocks of tissue cut for the microtome's 

 floor as well as the cut sections were suspended in Ringer's solution 

 cooled to 1-4C. As in the preceding work of this series the frozen 

 sections were cut sufficiently thin so that practically all of the 

 colloid or intercellular fluid was dissolved out of the acini as soon 

 as the sections were suspended in cooled Ringer's solution. By 

 centrifugalization the cells were separated from the colloid dissolved 

 in the Ringer's solution and carefully dried over an electric hot- 

 plate and then in an electric drying oven. Control pieces of 

 uncut whole gland were also dried in the same manner. Through- 

 out this paper colloid iodine solutions refer to cell-free solutions of 

 thyroid intercellular fluids obtained by the method just described 

 and dissolved in Ringer's solution. In all of the experiments the 



