328 Distribution of Iodine in Thyroid Gland. II 



From the results given in Table II one sees that the ratio of 

 iodine concentration in cells to iodine concentration in whole 

 gland (and hence the ratio of iodine concentration in cells to 

 colloid-iodine concentration) has a quite constant value. In 

 some glands (Nos. 12, 19, 23, and 24), to be sure, the iodine con- 

 tent of the cell mass analyzed was so low that no ratio value 

 could be obtained. But in general, despite great variations in 

 the iodine content and morphology of the glands analyzed, the 

 ratio values change relatively little. These findings in the dog's 

 thyroid gland are similar to those of Tatum 1 in the beef, pig, and 

 sheep thyroid glands. A comparison of the ratio values in dif- 

 ferent animals is given below. 



Effect of Feeding Iodine. 



It was thought that perhaps ratio changes could be induced by 

 the administration of iodine or iodine compounds. Capsules 

 containing 1 gm. of potassium iodide or 2 drops of tincture of 

 iodine in starch were fed over varying periods of time. No more 

 than one capsule was given in 24 hours. The results of the 

 examination of the glands of animals so treated are given in 

 Table III. 



The ratio obtained from analyzing the cells and whole gland of 

 the thyroid glands of animals which had received varying amounts 

 of iodine or iodine compounds over periods of no less than 3 days 

 is practically the same as that of the animals which had received 

 no iodine. One gland (that of No. 16) gave an unusually high 

 value which I cannot explain. In view of the variations in mor- 

 phology and iodine content of the glands of the normal series 

 together with the quite constant ratio exhibited by that series, 

 it is not surprising that the ratio still remains constant despite 

 the feeding and consequent absorption of iodine. From a con- 

 sideration of the glands examined it appears that the ratio is not 

 altered by the feeding of iodine as potassium iodide or free iodine 

 over periods of time ranging from 3 days to 3 weeks; and yet 

 the total iodine content of these glands undoubtedly is greatly 

 increased during that same period. 



