Standardization of potency of antirachitic substances by rat assay has, with the introduction of antirachitic agents other than cod liver oil or its concentrates, lost much of its value through the discovery that the relative prophylactic amounts of these different substances for rats, chickens and infants are not comparable unit for unit. No such dissimilarity was suspected during the time that irradiated products were first being developed until it was found that viosterol, when used for rats, chickens and infants, fell entirely out of line with what was known concerning the preventive dose of cod liver oil for the three species1 named. Irradiated milk now seems to be demanding a still further revision of ideas concerning vitamin D effectiveness2 as measured in rat units. While viosterol measured in rat units when compared to cod liver oil seems relatively impotent,3 for infants irradiated milk seems to be just
BARNES DJ. RICKETS: CONTROL WITH FIFTY UNITS (STEENBOCK) OF COD LIVER OIL VITAMIN D CONCENTRATE IN MILK. Am J Dis Child. 1934;48(6):1258–1267. doi:10.1001/archpedi.1934.01960190078008
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