170 HARRY BENJAMIN VAN DYKE 



but observed no exophthalmos, tachycardia or respiratory hippus in 

 their animals. There was no apparent difference either grossly or his- 

 tologically in the lobes of the thyroid gland on the operated and the non- 

 operated sides. Troell (10) reported that he was unable to produce 

 either exophthalmos or respiratory hippus by suturing the proximal end 

 of the phrenic nerve to the cervical sympathetic nerve. Employing 

 cocaine as a sensitizer for sympathetic nerve endings, Mills (11) did 

 not observe, following the repeated injection of cocaine, any alteration 

 in the amount or nature of the thyroid secretion as judged by what is 

 known of the gland's histology. Finally Rogoff (12) records one experi- 

 ment in which he drew blood from a vein of the left lobe of the thyroid 

 gland and at the same time stimulated the cervical sympathetic nerve 

 on that side in the hope of increasing the secretory activity of the stimu- 

 lated lobe. From the right lobe he also collected blood by way of a 

 vein. While drawing the blood he massaged the right lobe to some 

 extent but did not stimulate the right cervical sympathetic nerve. He 

 found that specimens of dried blood from each lobe were potent when 

 fed to tadpoles. But he could detect iodine chemically only in the 

 blood from the non-stimulated lobe. Moreover the non-stimulated lobe 

 had a lower iodine content than the stimulated lobe. 



In connection with some studies on the distribution of iodine in cells 

 and colloid in the thyroid gland I attempted to alter acutely the total 

 iodine content of the gland by stimulating the vago-sympathetic nerve 

 of the dog. Some inconsistencies in the results in the early part of 

 the work forced me to investigate the matter more carefully and to 

 repeat the work of Rahe et al. (2) and of Watts (3). 



Methods. Dogs were used in all of the experiments. All except 

 those whose numbers are above that of no. 78 were given daily feedings 

 of iodine over a period of one to eleven days. The daily feeding con- 

 sisted of a capsule containing two drops of tincture of iodine in starch. 

 In the animals fed iodine the stimulation of the vago-sympathetic nerve 

 was undertaken from two to ten days after the last feeding of iodine. 

 Throughout the experiments the animals were lightly anesthetized with 

 ether. Platinum wire electrodes were applied to opposite sides of the 

 carefully isolated vago-sympathetic nerve and shielded from all sur- 

 rounding tissues by glass. In all of the experiments except those re- 

 corded in table 5, a tetanizing current from three to six times as strong 

 as that sufficient to bring about a pupillary dilatation and apparent 

 protrusion of the bulbus oculi was employed. The regulation of the 

 strength of the current was made possible by a rheostat inserted in the 



