414 W. W. SWINGLE 



Topfer and Jolin) and yet such individuals remain healthy may 

 be explained by assuming that the tissues of such animals assimi- 

 late directly the iodin taken into the body, leaving no surplus to 

 be collected by the thyroid. Since the tissues of thyroidec- 

 tomized tadpoles can take up iodin in large quantities and use 

 it, there seems nothing inherently improbable in the suggestion. 



According to Voegtlin and Strouse, iodized amino-acid when 

 fed to tadpoles accelerates the metamorphosis of the animals, 

 but fails to replace the function of the thyroid in pathological 

 cases where there is a deficiency of thyroid function. 



The work of these authors, in so far as the acceleration of 

 metamorphosis is concerned, agrees with the results obtained in 

 the present experiments. The function of the thyroid in patho- 

 logical cases, however, may be an entirely different question. 



SUMMARY AND CONCLUSION 



1. Iodin and its compounds when fed to the larvae of Rana 

 pipiens and Bufo lentiginosus stimulate metamorphosis in these 

 animals very rapidly. 



2. Inorganic iodin when fed to thyroidless larvae of Bufo 

 lentiginosus brings about metamorphosis in an abnormally short 

 time. 



3. Iodin appears to function within the organism as a hormone 

 itself without the intermediation of the gland. 



4. The suggestion is made that the extraction of iodin from 

 the blood and its storage is the chief function of the thyroid gland. 



