In 1924, Steenbock, Nelson and Black demonstrated that a diet complete except for vitamins A and D caused cessation of growth before the appearance of xerophthalmia. They stated that irradiation of the animals would stimulate growth. In 1924, the irradiation of animals, foods and oils with the quartz mercury vapor lamp attracted worldwide attention and stimulated much work and investigation.
In 1925, Green and Mellanby showed that fat-soluble vitamin A acts as a protection against infection, and that numerous common infections occur in animals in the presence of a deficiency of this vitamin. The addition of fat-soluble vitamin D to diets deficient in vitamin A made little or no difference in the frequency of such infections.
In 1925, Steenbock, Hart, Hoppert and Black claimed that irradiated milk was more effective and rapid as an antirachitic agent than direct irradiation of the animal itself, and that the irradiation of butter destroyed