portant because in America people suffer much more from the "hidden 

 hungers" of moderate deficiencies than from the so-called "deficiency dis- 

 eases" (see table, pp. 132-133). 



From a chemical point of view, little can be said about vitamins as a 

 group, for each has distinct and specific characteristics and effects. Dis- 

 covering a new fact about one vitamin gives no reason for presuming that 

 it will be true of any of the others or of vitamins in general. But we are 

 likely to group the vitamins when thinking of nutrition, since they were dis- 

 covered in a relatively short time through feeding experiments with animals. 



In the early attempts to measure the quantity of a given vitamin neces- 

 sary for health, experimental animals were fed on carefully prepared diets. 

 The first standard unit was developed by Dr. Henry C. Sherman 

 (1875- ) of Columbia University, as "the smallest amount of vitamin C 

 sufficient to keep a guinea-pig of definite age and weight free from scurvy 

 for from 70 to 90 days". 



As research continued, several vitamins were identified as specific chem- 

 ical compounds. So it becomes possible to make direct chemical tests in 

 place of the long tests with living animals. Thus, Albert Szent-Gyorgyi 

 (1893- ), the Hungarian scientist, now living in the United States, in 1932 

 identified vitamin C as a definite chemical substance, ascorbic acid. The 

 following year some Swiss chemists produced this acid synthetically. It was 

 then possible to ascertain the amount of vitamin C, or ascorbic acid, in a food 

 by measuring the bleaching effect on a dye. Sherman's "unit" is accordingly 

 recognized as being equivalent to about 0.75 milligram of ascorbic acid. 

 During the Second World War, Russian scientists demonstrated what the 

 Canadian Indians knew four hundred years earlier, by a different name. 

 They showed that the leaves of pines and other evergreen trees contain small 

 quantities of vitamin C, which they were able to extract economically for 

 the use of armies and civilian populations that could not easily get citrus 

 fruits or tomatoes (see page 103). 



The Sources of Vitamins For generations, cod-liver oil was used in 

 European countries to help children through the dark days of winter, 

 nobody knowing just what made this rather unpleasant stuff so valuable 

 until vitamins A and D were discovered in our own time. During the 

 Second World War it became impossible to get supplies of this oil, but 

 almost immediately a new industry developed off the eastern shores of 

 Florida — that of catching sharks for the oil in their livers. Incidentally, 

 every bit of the animal is used in one way or another, from the hide, made 

 into tough leather, to the last scrap of flesh used for dog food, poultry food 

 and fertilizer. 



Vitamins seem to have their beginnings in plants. Vitamins present in 

 animal tissues are derived from plants or from substances formed in plants. 



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