DISTRIBUTION OF IODINE IN THYROID GLAND 173 



Hence it was thought desirable to analyze not single blocks or sam- 

 ples of dried powdered mixtures of whole gland but to analyze the whole 

 gland in each case. In experiments in which this last mentioned tech- 

 nique was employed the whole gland was carefully cleaned of connec- 

 tive tissue and blood vessels, and thoroughly dried first over an electric 

 hot plate and then in an electric oven. After two to three hours' dry- 

 ing in the electric oven the gland was broken into several pieces whose 

 weight was about 0.5 gram each and whose number therefore depended 

 on the size of the gland. The iodine determinations were made accord- 

 ing to the method earlier described by Kendall (13). By analysis of 

 powdered thyroid of known iodine content the accuracy of the method 

 (to about 0.008 mgm. of iodine) and the purity of the reagents used 

 were frequently examined and found to be satisfactory. 



The strength of the current employed in all of the experiments re- 

 corded in table 2 was three times that sufficent to cause dilatation of 

 the pupil and apparent protrusion of the bulbus oculi. Both the stimu- 

 lated and the non-stimulated vago-sympathetic nerves were cut in 

 two places: at a point in the neighborhood of the eighteenth tracheal 

 ring and also at a level a little above that of the hyoid bone. The reason 

 for cutting the non-stimulated nerve in such a manner was to eliminate 

 the possible effect of tonic secretory impulses on the non-stimulated 

 lobe. The vago-sympathetic nerve was stimulated a little above the 

 point at which it was cut low in the neck. In the above experiments 

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

 in whole gland was determined by a method previously described (14). 

 From the data given in table 2 it may be seen that stimulation of the 

 vago-sympathetic nerve under the conditions described is without ap- 

 preciable effect on either the ratio value or the concentration of iodine 

 in the whole gland. 



When it was found that there was no consistent diminution in the 

 concentration of iodine in the stimulated lobe only the stimulated 

 vago-sympathetic nerve was sectioned in the manner described above. 

 In experiments 76, 79 and 80 a strength of current six times that neces- 

 sary to cause ocular changes characteristic of sympathetic stimulation 

 was used; in all of the other experiments to be found in table 3 the cur- 

 rent was of the same strength as that used in the experiments recorded 

 in table 2. From the standpoint of the iodine concentration in whole 

 gland the results given in tables 2 and 3 are very similar. Stimulation 

 apparently has no effect on the concentration of iodine in the stimulated 

 lobe. 



