PRESENT-DAY KNOWLEDGE OF VITAMINS 



103 



non-deposit of the mineral calcium which is present in certain 

 foods. The head of a rachitic animal usually becomes bulky, and 

 the bones at the knees and ankles, become enlarged. For experi- 

 mentation, a set of rats was fed a diet which contained vitamin A, 

 but lacked another substance known as vitamin D; another set 

 of rats was given vitamin D in the form of cod-liver oil. The first 

 group developed rickets ; the second group grew normally. Many 

 physicians and scientists have observed and reported that the 

 exposure of rachitic children to the rays of the sun has brought 

 about an improvement and cure of rickets. In these cases there 

 were plenty of calcium and phosphorus already present in the 

 blood, and the sunlight is thought to have influenced, in some 

 wav, the activities of certain cells so 

 that they could make efficient use of 

 these minerals. Other scientists have 

 found that it is the ultra-violet rays in 

 sunlight, which are instrumental in 

 preventing and curing rickets. These 

 curative rays cannot pass through 

 ordinary window glass, but will pass 

 through quartz glass. 



If babies are given food deficient in 

 vitamin D, but whrch has been exposed 

 to these light rays, the food can be 

 activated so as to cause it to have the 

 same effects as the ultra-violet ravs. 

 Cotton-seed oil, which ordinarily con- 

 tains no vitamin D, becomes anti- 

 rachitic when exposed to sunlight. 



Two scientists, Evans and Bishop, 

 have added another member to the 

 vitamin family. They found that this vitamin, which thev named 

 vitamin E, has a marked influence upon the fertility of rats. 



Sunsuits give children the benefit of 

 the direct rays of the sun. 



