H. B. van Dyke 17 



Even here considerable iodine as KI was still bound by the glands 

 which had taken up some colloid iodine. These results suggest 

 that the colloid iodine, bound but incompletely synthesized into 

 active principle, is in a more diffusible form in the acutely iodized 

 gland than in the more normal resting gland. Moreover, the 

 incompletely synthesized active principle may be more readily 

 split by hepatic action (7) into simpler products (e.g., iodides) 

 which are then bound by the hyperplastic thyroid gland. 



Marine and Rogoff (3) declare that even 30 hours after intra- 

 venous administration of a solution of KI very little of the thyroid's 

 active principle, as measured by the effects of thyroid on tadpole 

 growth and metamorphosis, has been elaborated. The less 

 diffusible and less readily split normal colloid iodine compound 

 (Table II) probably represents the more fully elaborated active 

 principle. 



SUMMARY. 



The findings of Marine and Feiss and Marine and Rogoff that 

 the hyperplastic thyroid gland of the dog rapidly bincls iodine 

 intravenously introduced as a solution of KI were confirmed. 



By a method already described (5) the ratio value of iodine in 

 cells to iodine in whole gland was determined and found to be very 

 low after the intravenous injection of KI solution into dogs with 

 hyperplastic glands when those glands were removed 1.5 to 60 

 minutes after the injection. The ratio value more nearly ap- 

 proached the normal if the interval elapsing between injection 

 and removal of gland was made about 24 hours instead of 1 hour 

 or less as in most of the experiments. This finding is in keeping 

 with the histological changes described by Marine and Rogoff in 

 such glands 20 hours after the intravenous injection of KI solution. 



When iodine as colloid iodine solution of normal animals was 

 administered intravenously practically none of the colloid iodine 

 was taken up by hyperplastic glands during the periods of time 

 used in these experiments; yet from an injection of a comparable 

 amount of iodine in the form of KI the ready binding of iodine by 

 similarly hyperplastic glands was proved. Colloid iodine of 

 hyperplastic glan'ds removed 1 hour after the intravenous injection 

 of KI solution was taken up to some extent by hyperplastic glands; 

 but these last named glands bound additional iodine as KI intro- 



