DIET AND NUTRITION 



white vegetables, such as the potato, white turnip, 

 apple, etc. 



Vitamin A. This substance is now identified with the 

 yellow pigment of vegetable foods, a compound known as 

 carotin, from its abundance in carrots; or at least it seems 

 to be demonstrated that carotin is the mother substance 

 of the vitamin into which it is readily converted in the 

 body. The latter seems the more probable, since the liver 

 of an animal may be nearly freed from vitamin A by feeding 

 a diet free from it, and become rich in the vitamin when an 

 abundance of carotin is provided. Such a liver is still nearly 

 free from yellow pigment. This is interpreted as meaning 

 that the yellow pigment is converted into the vitamin, 

 and is not itself the vitamin A. It has recently been stated, 

 on experimental evidence, that plants are all practically 

 free from the vitamin A, but that they furnish carotin from 

 which it is made in the body. Liver fats, egg yolk fats, and 

 cod liver oil contain the vitamin instead of carotin. Little 

 is known about the chemical nature of carotin and less 

 about that of vitamin A. The former is a highly unsaturated 

 hydrocarbon containing 40 carbon and 56 hydrogen atoms 

 in its molecule. It is an unsaturated molecule and takes on 

 oxygen readily, losing in the process its yellow color and 

 its value as the mother substance of the vitamin. 



Effects of Deficiency of Vitamin A. Much research has 

 been done on the effects of deprivation of animals of this 

 vitamin. The injury to the body which results from this 

 kind of specific starvation is limited to the epithelial 

 tissues. Since these line the ducts of the tear glands, 

 salivary glands, and other digestive glands, and constitute 

 other glandular tissues of major importance, vitamin A 

 deficiency quickly undermines health. The epithelial cells 

 keratinize, becoming like the outer layers of the skin, and 

 lose their normal functions. Plaques of these cells desqua- 

 mate and tend to plug the ducts of glands. In vitamin A 



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