FAT-SOLUBLE VITAMINS

Abstract

Last year Steenbock and Nelson (1) laid the foundations for an experimental method in which, by the use of ultra-violet light, growth can be used as a measure of the comparative amounts of vitamin A occurring in any food.Their method also allows demonstration, in case of inhibited growth and in the absence of a vitamin A deficiency, as to whether this inhibition is due to lack of the antirachitic vitamin or some other factor.Preliminary data on the use of this method have already been presented (2).In attempting to use this method for determinations of vitamin A in butter a large series of experiments was run in which eight groups of rats, six animals to the group, were used (3).In each group two animals were exposed to ultra-violet light from a quartz mercury vapor arc, with the expectations that if there were a deficiency of the antirachitic vitamin in the ration, the two irradiated animals would, by their increased growth, reveal such to be the case.It merely remained, then, to find out at what level of butter fat irradiation no longer had any effect.This would be the level at which the butter furnished a sufficiency of the antirachitic vitamin.Contrary to what was expected, all the animals in each group,