DISTRIBUTION OF IODINE IN THYROID GLAND 169 



changes in the gland on the stimulated side. Watts likewise found 

 that he could reduce the iodine content of the right or left lobe of the 

 thyroid gland of the dog by stimulating the "cervical sympathetic iso- 

 lated from the vagus sheath" and the "nerve filaments accompanying 

 the superior thyroid vessels." However Watts maintained that he 

 could cause some diminution in the iodine content simply by periodi- 

 cally reducing the blood flow through the gland by "occluding the main 

 thyroid artery" the nerves of which had been dissected away. Hence 

 he concluded that all of the effects of stimulation on the iodine content 

 can be accounted for by the coincident vasomotor changes which he 

 showed to be present. 



Positive evidence of the secretory effect of sympathetic stimulation 

 has been reported by Cannon and his co-workers (4) in several communi- 

 cations. Working with cats they sutured the phrenic nerve with the 

 cervical sympathetic nerve and observed following the operation in- 

 creased basal metabolism, respiratory hippus and falling hair which 

 they interpreted as the results of hypersecretion of the thyroid gland 

 caused by the periodic bombardment of the gland by impulses carried 

 from the respiratory center to the gland's secretory nerves. Cannon 

 and Cattell (5) adduced additional evidence as to the role of the sympa- 

 thetic nerves in experiments dealing with the electrical condition of the 

 gland. Following the stimulation of the upper thoracic sympathetic 

 nerves or the injection of epinephrin they were able to show a definite 

 action current in the thyroid gland after a latent period of five to seven 

 seconds. Recently Cannon and Smith (6) maintained that gentle mas- 

 sage of the thyroid gland or stimulation of the cervical sympathetic 

 nerve increases the rate of the denervated heart. The denervated 

 heart is said not to be affected when the cervical sympathetic nerve is 

 stimulated after removal of the thyroid gland. Moreover Levy (7) ob- 

 served that the pressor effect of epinephrin after a variable latent period 

 is increased by the stimulation of the cervical sympathetic nerve. He 

 declared that stimulation of the cervical sympathetic nerve has no such 

 effect after thyroidectomy. 



However the conclusions based on the experiments mentioned above 

 have not been universally accepted. Burget (8) was unable to alter the 

 thyroid gland noticeably either by uniting the phrenic and cervical 

 sympathetic nerves or by removing a section of the cervical sympathetic 

 nerve. Marine, Rogoff and Stewart (9) sutured together the phrenic 

 and cervical sympathetic nerves in several cats. They demonstrated a 

 functional union between the phrenic and .cervical sympathetic nerves 



