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





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Ki(;..S6. — .Section of wiUi Wisconsin brook trout from <^anie experiment. Xatiinil food 12 months. Noniial thyroid. XS6. 











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Kic. S7. — Section of wild Wisconsin brook trout. Cooked liver feeding 12 montlis. Normal lh\roid. XS6. 



