THYMUS AND THYROID GLANDS. 351 



weighing 550 mgr. air dry, contained about 0.25 mgr. iodine, 

 while no iodine could be detected in the large thymus weighing 

 over two grams, air dry. 



Although it may be questioned whether the minute traces 

 of iodine found by Baumann on analysis of a very large quan- 

 tity (200 grams) of thymus deserve the physiological signifi- 

 cance frequently attributed to this single observation, I have 

 repeated these experiments with large quantities of thymus. 

 The fresh glands (calves') were dissected very carefully, and 

 after treatment with absolute alcohol and ether were tested by 

 the method already referred to. Thus in one experiment 213 

 grams of fresh thymus (yielding 39 grams dry substance) 

 were examined with negative results; similar experiments 

 were made with varying quantities of substance, but in no 

 case could iodine be detected in this material. In two samples 

 of desiccated thymus carefully prepared for me by Armour and 

 Company, I have likewise been unable to find a trace of iodine, 

 even when krge quantities were fused; while I have not failed 

 to detect very small quantities of iodine added to equally large 

 amounts of the same desiccated material. 



In two samples of commercial thymus preparations, how- 

 ever, I have detected traces of iodine. Nine grams of one of 

 these, labelled "Desiccated thymus containing 50 per cent 

 sugar of milk," showed a faint trace of iodine ; another pro- 

 duct " Desiccated thymus of the calf," repeatedly yielded about 

 0.07 mgr. iodine in twelve grams of the substance. In these 

 cases the iodine found presumably was attributable to contam- 

 inating materials. Additional weight is lent to this view by 

 the fact that of three commercial thymus preparations from 

 the same source, only one showed traces of iodine ; while one 

 of the two iodine-free products had been prepared at my sug- 

 gestion with particular care to avoid contamination with 

 accessory thyroid bodies. 



From the foregoing evidence it seems probable that iodine 

 is not a normal constituent of the thymus and that Baumann's 

 detection of that element in the gland was due to admixture 

 of thyroidal tissue. Finally, the feeding experiment of 



