They seem to "regulate" or balance some of the protoplasmic activities, as 

 certain minerals do. 



Each vitamin was first known by its effects on metabolism, and not at 

 all by its chemical nature. Investigators labeled the "unknown something" 

 present in milk, but not present in a diet of pure nutrients, "A". The 

 "unknown something" lacking in polished rice and resulting in beriberi 

 and polyneuritis wheti it wasn't there, was called B. That which was lack- 

 ing in food that brought scurvy was named C. As new discoveries were 

 made, additional letters were used to designate the unknown factors. Some- 

 times different investigators used the same letter to designate different sub- 

 stances. Even today our letter designations are somewhat confusing. 



Naming the Vitamins Early in the study, the vitamins were separated 

 into two groups, those soluble in fats and those soluble in water. Feeding 

 experiments yielded at first contradictory results because, as was later found 

 out, the different fat-soluble substances are unevenly distributed in various 

 foods. Accordingly the results were due in some cases to a deficiency of one 

 factor, and in some to a deficiency of another. In 1922 the fat-soluble ex- 

 tract, then called A, was clearly separated into two distinct factors, now 

 called vitamins A and D. Similarly, in the water-soluble extract then called 

 Bj a dozen or more factors have been identified by their metabolic effects. 



In America the first two factors isolated from the original B extract 

 were called vitamins B and G. In England these same factors were known 

 as Bi and B2. Later, vitamin G or B2 was found to include two or more 

 factors. Sometimes the name was applied to riboflavin, a substance found 

 in plants, sometimes to a product formed within the animal body by a 

 union of riboflavin with another unknown substance. Some of the bodily 

 disorders originally attributed to the lac\ of vitamin G (for example, the 

 disease pellagra) were found to result from a lack of niacin. 



As more vitamins came to be recognized without reference to the orig- 

 inal fat-soluble extract or water-soluble extract, they were designated by 

 additional letters in the alphabet. Thus, vitamin E was discovered during 

 studies on the ripening of eggs in rats, and vitamin K was discovered in the 

 study of the clotting of the blood. As we have come to know the chemical 

 make-up of the various vitamins, we have substituted chemical names for 

 the former letter designations. Thus vitamin B becomes thiamin, vitamin C 

 ascorbic acid, and so on (see table, pp. 132-133). 



Differentiating the Vitamins Most of the vitamins were discovered in 

 connection with diseases that developed in their absence. We have accord- 

 ingly come to think of them as anti this and anti that. In fact, we have 

 anti-names for most of them, as well as the alphabet names. It would be 

 more helpful, however, to think of the positive values of vitamins in nor- 

 mal metabolism than of the effects of their absence. This is especially im- 



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