The failure of rats to develop rickets on a diet deficient in Vitamine A

The fat-soluble vitamine, or a vitamine closely associated with it, is regarded by some as being equivalent to an antirachitic vitamine; the development or non-development of rickets is thought to be dependent mainly on the absence or presence of this factor. In a previous report one of the writers has stated it to be his opinion that this relationship does not hold true for human rickets. The following experiments were planned to ascertain whether a diet markedly deficient in this vitamine led to the development of rachitic lesions in young rats; for this purpose rats weighing about 30 g. were put on a diet of extracted casein 21 per cent., rice starch 57 per cent., salt mixture 5 per cent., Crisco 17 per cent., yeast extract (Osborne and Wakeman) 60 mg. a day. The casein was extracted by means of ether and cold alcohol. The salt mixture was that employed by Osborne and Mendel. Thirty-five rats in all were used for this experiment. They were kept on this rigid diet for a period averaging about three to four months, but extending in several cases five to six months. In no instance were rachitic lesions noted either microscopically or macroscopically, merely an inactive osteogenesis. That the dietary in point of fact did contain only a minimal amount of the fat-soluble vitamine was proved by the lack of gain of the animals after they had been on this food mixture for about sixty days, by their prompt response in growth on the addition of 6 per cent. of butter fat to the diet, and by the development of ophthalmia or keratomalacia in almost all of the animals and its rapid subsidence on adding butter to the dietary.