514 PROTOPLASM 



Vitamin A. — A disease of the eyes known as night bUndness 

 and subsequently called by McCollum "xerophthalmia" was 

 by Osborne and Mendel demonstrated to be due to a deficiency 

 in diet. McCollum and Simmonds then found that diets lacking 

 in butterfat cause the disease. The specific substance present in 

 butterfat which prevents the disease is vitamin A. Its absence 

 also prevents normal growth, and so it is known as the "growth 

 substance." (Actually, normal growth depends upon the 

 presence of 30 or more indispensable nutrient substances.) 

 Other important disturbances resulting from the lack of vitamin 

 A are lowered resistance to infections, diseased condition of the 

 kidneys, disturbance of oestrous cycle and lactation, retardation 

 qi growth, sterility, etc. 



The most potent natural sources of vitamin A are halibut and 

 cod-liver oil, but the vitamin is abundant in milk, egg yolk, 

 butter, carrot, lettuce, etc. It is produced in the body through 

 conversion, by the liver, of carotene, C40H66, the yellow pigment 

 in vegetables (particularly carrots and corn), fruits, and butter. 



Vitamin B. — Vitamin B holds the historical position of the 

 first vitamin studied which led to the coinage of the word. Its 

 absence usually causes beriberi, common among rice eaters of the 

 orient, although polyneuritis may also result as well as injury 

 to nerve tissues, loss of appetite, and impairment of digestive 

 processes. The chemical constitution of vitamin B is undeter- 

 mined, although it is known to be a nitrogenous base. Knowl- 

 edge of its true physiological effects is complicated by the fact 

 that it is usually accompanied by the second component — 

 vitamin G (vitamin B2). 



Vitamin B is widely, though sparingly, distributed in plant 

 and animal material. It is most abundant in yeast and the 

 embryos of grains (wheat, barley, etc.). The vitamin B in 

 cow's milk is insufficient for infants; it must, therefore, be supple- 

 mented (by the tenth day). 



Vitamin C. — Vitamin C is best known for its antiscorbutic 

 properties. Scurvy appears to be limited to man, monkeys, and 

 guinea pigs. It is most readily produced in guinea pigs by a 

 diet of cereals and bread. The addition of fresh vegetables cures 

 the disease. 



Vitamin C is almost solely a plant product. It is abundant in 

 paprika, red capsicum, and lemon and orange juice and is found 

 in cabbage, lettuce, and celery. 



