A distinct seasonal variation in the antirachitic action of sunlight has been demonstrated by Tisdall and Brown at Toronto.1 Similar variations have been shown in the ultraviolet intensities of sunshine at Baltimore2 and Chicago3 by photochemical rather than by biologic methods. On the other hand, Lewis, Frumess and Stein4 have recently published data showing no such variation in the sunshine at Denver. The experiments on this subject published prior to 1930 together with the various methods employed have been carefully reviewed by Blunt and Cowan.5
Although severe rickets is less commonly found in the southern states than in northern cities, the incidence is far greater than can be justified in the light of the present knowledge of the etiology and prevention of this disease. Williams6 wrote in 1928: "Severe rickets is extremely rare in New Orleans and vicinity, but a mild form of the
DAY PL. SEASONAL VARIATION IN ANTIRACHITIC ACTION OF ARKANSAS SUNSHINE. Am J Dis Child. 1932;43(6):1455–1460. doi:10.1001/archpedi.1932.01950070024002
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