374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



play all day long in the sunshine. Recognizing the success of her 

 method, the authorities presented her with a few very crippled 

 children and a donkey cart in which she could drive them to the 

 beach. As this experiment proved successful, a large hospital was 

 built on the beach with a good surgeon as director. But the children 

 in the hospital did not improve as rapidly as under Madame 

 Duhamel's care, since they were kept in bed in large rooms and when 

 playing in courtyards their coats were never removed. 



Later Dr. Bonnet, in the middle of the nineteenth century, noticed 

 that joint tuberculosis improved by exposure to sunlight. After him 

 a succession of surgeons and doctors noticed the effect of sunlight 

 treatment on patients, until finally sun treatment was adopted every- 

 where in Europe. 



Why is sunlight so beneficial in the treatment of invalids? And 

 why are people who live most of their lives in the open air and 

 sunshine able to build up a great immunity to disease? What is 

 there in the sun's rays that promotes health and well-being? 



Beyond Newton's seven visible rays of the spectrum, which may be 

 separated in a sunbeam by a prism, are certain invisible rays which are 

 of vital importance to life on earth. These rays are shorter in 

 wave length than the visible violet rays, so they are called ultra- 

 violet rays. Only a very small quantity of these rays — a trifling per- 

 centage of the total — is present in the sunlight that reaches the earth. 

 There is a much larger quantity of them outside the earth's atmos- 

 phere, but the ozone formed from oxygen in the upper layers of the 

 atmosphere by the action of these ultraviolet rays serves as a ray 

 filter that protects the life on the surface of the earth from these 

 shorter rays which have been proved to be very destructive to tender 

 tissues. 



After the sun treatment, or heliotherapy, had been generally 

 adopted, and since it was difficult to find sunshine in winter in all 

 places, an artificial source of ultraviolet rays seemed desirable to 

 replace the missing sunshine. The quartz lamp is generally used 

 in hospitals under medical supervision for this purpose. 



Alfred Hess, who succeeded in explaining scientifically the ef- 

 ficiency of sunshine, noticed that rickets is very frequent among 

 babies born in winter or in the autumn, due to the fact that they 

 are kept indoors without enough sunlight. He succeeded in induc- 

 ing rickets in rats with a rachitic diet and discovered that they got 

 rickets only when kept all the time in complete darkness, and that, 

 with the same diet, they were protected from rickets if exposed for 

 about half an hour each day to the sun. The rats with rickets, 

 when in cages with rats treated with sunshine, cured their rickets 

 by eating the excrements of the sunshine-treated rats. In other 



