A Method for the Biological Assay of Cod Liver Oil

Standardizationof cod liver oil for medicinal purposes was at first made with respect to vitamin A content (I) and growthpromoting properties (2).More recently, however, interest has centered in the vitamin D content of the oil, and biological tests are directed toward determinations of antirachitic potency.Methods for such a biological assay are indicated by the facts established in recent years during the course of investigation relative to rickets.Of importance was the finding that a condition simulating human rickets could be established experimentally in rats and other animals by feeding certain deficient diets.Diets containing calcium and phosphorus in disproportionate amounts, particularly those of high calcium-low phosphorus type (3), gave rise to rachitic developments, provided that at the same time vitamin D was absent from the diet.Cod liver oil, which had been prescribed for years as a curative for rickets, was now shown experimentally to be particularly rich in the antirachitic factor which functions in the prevention or healing of rickets induced by an unfavorable dietary regime.Moreover, it was established that ultra-violet rays had the same effect as cod liver oil in preventing or curing rickets.Histological study of the rachit,ic bone indicated that very definite changes took place even before gross lesions were distinctly