Abstract
Information upon the amount of radiation needed to cure rickets with respect to the area exposed is very meagre. Maughan and Dye 1 have shown that in chickens only a small amount of radiation is necessary to cure rickets and that the area covered by the feathers receives very little or perhaps none of the beneficial rays.
Eighteen rats at 4 weeks of age were put upon the Steenbock rachitic diet 2965 and after 21 days, having developed a severe degree of rickets, were ready for treatment. Treatment was continued for 21 days and degree of healing was judged by radiographic examination. As a source of ultraviolet radiation the General Electric Sunlamp with the Type S1 bulb was used. Previous studies had shown that exposure of the whole rat 30 minutes per day to the G. E. Sunlamp at 3 feet brought about complete healing of rickets in 3 weeks' time.
It was found that very little radiation is effective through the hair of the rat as an exposure of 2 square inches of unshaved back of the rat for 40 minutes daily produced only a beginning healing. Irradiation of the skin of the rat is much more effective as an exposure of one-fourth square inch of shaved back of rat for 20 minutes daily at 3 feet brought about complete healing of rickets in 3 weeks. Irradiation of this area of the skin produces greater healing of rickets than exposure of the whole animal for the same length of time. According to recent work of Diack 2 on the surface area of rats, this area of one-fourth square inch amounts to about one-eightieth of total surface area. It is surprising that such a small fraction of the total surface area of the rat can absorb sufficient of the rays to heal rickets.
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