If special proof were needed of the importance of an accurate standardization of therapeutic products prepared from natural resources without the refinement and chemical purification which applies to most of the inorganic compounds and alkaloids, for example, it would be found in the evidence furnished by recent studies of the very marked seasonal variation in the iodin content of the thyroid gland of different species of animals. We have already called attention to the work of Seidell and Fenger3 on this subject. These investigators have had exceptional opportunities to obtain suitable animal material for their studies, and have used products from the very places which serve as sources for the preparation of gland products in this country. Their findings in respect to the existence of seasonal variations have been verified in a general way by data obtained in England from sheep.4
A repetition of the analyses of the
SEASONAL VARIATION IN COMPOSITION OF THYROID GLAND. JAMA. 1915;LXIV(2):155. doi:10.1001/jama.1915.02570280061023
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