Bull. U. S. B. F. 1912. 



Platic CVII. 









^ Fig. 116. — Section of normal thyroid of adult female do^. mother of dogs 15. 16, 17. 2U. 21 and 12. u.sed as control for 

 dog 18. figure 117. Received same water but boiled before drinkingr. X16U. 



Fi<;. 117. — Section of markedly enlarged thyroid ot adult dog IS. Result after five months drinking water in which 

 were suspended scrapings from fish troughs in which carcinoma of the thyroid in trout was continually developing. X160. 



