DISTRIBUTION OF IODINE IN THYROID GLAND 



175 



stimulated in the neck at about the level of the fifteenth tracheal ring. 

 The current was of the same strength as that employed in the experi- 

 ments of table 2; each time the current was made there ensued a respira- 

 tory arrest and the ocular changes typical of sympathetic stimulation. 

 Again there was no consistent change in the concentration of iodine in 

 the stimulated lobe. 



TABLE 4 



The concentration of iodine in the lobes of the thyroid gland of the dog after the 

 stimulation of the intact v ago-sympathetic nerve on one side for a period of approx- 

 imately three hours 



Effect of vasomotor activity on the concentration of iodine in the thyroid 

 gland. It will be recalled that Watts (3) concluded from his experi- 

 ments that vascular changes will account for the diminution in the con- 

 centration of iodine which he brought about by stimulation of the cer- 

 vical sympathetic nerve. The experiments of table 5 were undertaken 

 to find out whether or not a slightly different type of stimulus sent into 

 the nerve at an interval more nearly like that employed by Watts had 

 an effect comparable to that found in the experiments previously per- 

 formed. It was also thought desirable to determine whether or not 

 the characteristic vascular changes were present throughout the 

 experiments. 



The technique except for certain features of the stimulation was the 

 same as that used in all of the preceding experiments. Usually the 

 stimulated vago-sympathetic nerve was ligated and cut at about the 

 level of the eighteenth to twentieth tracheal ring; near the ganglion 

 nodosum only the vagus nerve was cut. In all of the experiments the 

 sympathetic chain was intact above the eighteenth tracheal ring. The 



