MODERN SUN CULT STUBMER 203 



of it, and he practiced heliotherapy lonf]: befoi'e anything was i<no\vn 

 about vitamin D. It is interesting to know also that rickets is the 

 disease which he treated with sunlight. But since his day much 

 definite information has been brought to liglit, some of it by feeding 

 experiments conducted with animals, both in the absence and in the 

 presence of radiation. Curative procedures also have been engaged 

 in, experimentally on animals, and clinically on patients in hospitals. 



VITAMIN D 



It is now known that when the skin is irradiated with ultra- 

 violet, pigmentation or tanning is not the only result. Far more 

 important is the change experienced by a certain chemical substance 

 in the skin, a substance which becomes activated to form a vitamin, 

 namely, the vitamin now designated as vitamin D, which appears 

 to be just as essential to the proper functioning of the human organ- 

 ism as is certain mineral matter which, it is well known, we must 

 supply in our diet. If, then, we receive, because of our abnormal 

 modern conditions of life, too little sun radiation, the tiny labora- 

 tories in our skin fail to elaborate an adequate supply of vitamin D, 

 and as a result, the life functions fail to go on normally and as they 

 should, even though we may not develop a recognizable disease. 



BOTTLED SUNSHINE 



We may in such cases proceed in a manner suggested by the serum 

 treatments. We may obtain from another living organism the sub- 

 stance which we fail to produce ourselves. If we cannot develop our 

 own vitamin D, we may buy it, and take it as medicine or food. Now 

 the codfisli, and other fish also, possess an abundance of vitamin D, 

 the source of which appears to be the marine algae, which are eaten 

 by shrimp and small fish, which in turn supply the vitamin much 

 against tiieir will to the larger fish. The vitamin D in fish is found 

 principally in the liver, and it occurs in the oil expressed from fish 

 liver. So cod-liver oil has come to be known as '' bottled sunshine " 

 useful in the treatment of the diseases which develop because of an 

 inadequacy of solar radiation. 



HOW MUCH SUNSHINE IS ENOUGH 



But what amount of such radiation and how much ultra-violet 

 is adequate? We do not know. Physicians recognize the diseased 

 conditions which follow a dearth of sunlight but they cannot tell 

 us precisely how much we must have. Hence we do not know how 

 long we must be in the sunlight, how great an area of our body 

 surface must be exposed to it, nor how long we can go on without 

 irradiation. But we do know that in the winter at least we do not 

 receive as much as we need. 



