BULL. U. S. B. F. 1912. 



PLATE CVII. 



Fie;. 116. -Section of normal thyroid of adult female dog. mother of dogrs 15. 16, 17, 20, 21 and 22, used as control for 

 dogr 18. figure 117. Received same water but boiled before drinking. X160. 



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Fit;. 117. Section of markedly enlarged thyroid of adult dog 18. 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. 



