Studies in the Chemistry of Vitamin A. by Osman Horace Cady and James Murray

The animals used in the research were standard albino rats and a strain of hooded rats which had been inbred for a number of years. The stock members of the colony were maintained on Steenbock’s ration (2) except that bone ash was substituted for calcium carbonate in accordance with later recommendations of the author. Fresh, whole milk was given ad Zibitum. Litters were reduced to six animals. In testing for vitamin A the growth method of Drummond and Coward (3) and the curative method of Steenbock and Coward (4) were employed. The basal vitamin A-free ration consisted of fatfree heated casein, 18 per cent; dried yeast, 6 to 8 per cent; Steenbock’s Salts 40 (5), 4 per cent; dextrinized starch (6), 70 to 72 per cent; distilled water, ad libitum. The antirachitic factor was supplied by irradiation of the casein before a quartz mercury vapor lamp of the Hashimoto and Wu type (7). Later in the work the dextrin also was irradiated. The experimental diet consisted of the basal vitamin A-free ration in which the substance to be tested had been incorporated by adding it at the expense of an equal percentage of dextrinized starch. The progress or cure of the xerophthalmia was deter-