388 Fortieth Annual. Meeting 



cumulative agents much used against infectious disease, is 

 quite consistent with the theory of infection as the cause 

 of the enlargement. In the light of this, the fact that iodine 

 affects the thyroid tumor can hardly be an important argu- 

 ment against its cancerous nature. Many agents, including 

 chemicals, affect cancer cells and inhibit cancer growth, 

 particularly in early stages. 



Since iodine, mercury, and almost without doubt various 

 other chemicals, cause a reversion of structure and a 

 diminution in size of the tumor, some of them are possibly 

 a preventive, when properly administered, of the initial 

 enlargement and thus of the whole process of tumor growth, 

 but the demonstration of this is yet to be made. Iodine in 

 the form of potassium iodide can be readily added to the 

 water but on a large scale would prove expensive. To in- 

 corporate it with the food would be more economical and 

 a method of conveniently administering it without loss 

 could probably be found. Mercury is far more toxic than 

 iodine. Perhaps a more suitable substance than either 

 may be found. 



The thyroid tumor, either in its goitrous or cancerous 

 stage, as an enemy to fish culture is hardly a matter of the 

 first importance. The percentage of affected fish is usually 

 low, rarely does it take on the acute form of an epidemic, 

 growth can proceed even with the increase of the tumor, and 

 the fish breed without apparent hindrance. But it is a 

 rather sinister suggestion that fishes so much the subject of 

 artificial propagation and distribution as the chars and trouts 

 have either goiter or cancer, especially the latter. Goiter 

 in man is known as a dangerous often water-borne disease 

 and a certain per cent of cases develop into cancer, although 

 goiter is a disease of youth and cancer of maturity. It 

 does not add to the attractiveness of fish culture for the 

 public waters that these much sought and widely distributed 

 fish are subject to goiter. But when cancer is added there 

 is a sentimental if not a real reason for alarm. The cause 

 of cancer in any animal is unknown and therefore a fruitful 



