Abstract
The preventive influence of direct sunlight and of radiation with the mercury vapor quartz lamp upon the development of experimental rickets in rats has been demonstrated in experiments reported in previous studies. A logical further step was to determine whether or not direct sunlight and radiation with the mercury vapor quartz lamp would also prevent the development of xerophthalmia in rats fed diets which, under ordinary conditions of roomlight, would lead to the development of both rickets and xerophthalmia and of xerophthalmia alone. If this information could be ascertained it would be a valuable contribution to the study of xerophthalmia and by analogy would suggest either the unity or the divisibility of the factors contained in cod liver oil, which prevent and cure both xerophthalmia and rickets. It was desired also to determine whether or not different combinations or groups of light rays—as for example, direct sunlight, quartz lamp radiations and roomlight—have the same or similar influence upon rats fed xerophthalmia producing diets. It was conceivable also that complete absence of light rays might have a different effect upon experimental animals than that produced by radiations showing either a complete solar spectrum (direct sunlight) or spectra considerably different from sunlight (quartz lamp radiation and roomlight).
On October 22, 1921, fifteen young albino rats were placed on a diet low in fat-soluble A and phosphorus (3127). Previous experience had shown that young rats on this diet would develop rickets and xerophthalmia. The animals were divided into three groups of five each. One group was to be kept in a laboratory room screened with ordinary window glass; a second group was to be kept in total darkness, excepting for the rays from a red electric light bulb such as is used in photographic dark rooms 1 ; the third group was to be kept in ordinary room-light, but was to be radiated with a mercury vapor quartz lamp.
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