Abstract
In the course of studies on the comparative value of various light sources for the cure and prevention of rickets 1 a study was also undertaken to determine the seasonal antirachitic efficiency of sunshine in latitude 42° 39’(Albany). These experiments have been continued over a period of 2 1/2 years.
Rats at 4 weeks of age were put on the Steenbock rachitic diet 2965 and both the curative and preventive type of experiments were used. In the curative type of experiment the animals, having developed a severe degree of rickets within 21 days, were exposed to sunshine for varying lengths of time between 10 A.M. and 3 P.M. in the winter months and between 11 A.M. and 1 P.M. in the summer months. Treatment was continued for 21 days. In the preventive type of experiment the animals were exposed to the sun's rays for a period of 6 weeks from the time that they were put on the rachitic diet. Skyshine as well as sunshine was available in these experiments. No attempt was made to compensate for the cloudy days so that on cloudy days rats received skylight or reflected light from the clouds and sky. Several different dosages were tried in each type of experiment in order to determine the length of exposure required either to bring about complete healing of rickets within 3 weeks or to prevent the development of rickets. Diagnosis was based on roentgenograms. Along with these observations determinations of the ash in the dry fat-free extracted femurs were made and also in most instances the blood phosphorus.
In the curative experiments exposures of 240 to 270 minutes per day during the months of December and January showed very slight or no healing.
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