328 



ANIMAL BIOCHEMISTRY 



were required in small amounts by animals. At this time Funk coined 

 the term vitamine (the e is now omitted) to describe his vital nutri- 

 tional factor, which had the chemical properties of an amine. Now 

 the vitamins include several chemically unrelated groups of com- 

 pounds required for the well-being and normal ftuictioning of various 

 animal species. 



Even when nutritionists fully realized the possible occurrence of 

 essential factors, little progress was made at first in relating particular 

 physiological syinptoms to certain experimental diets. In 1906 Hop- 

 kins concluded that not only beriberi but scurvy and rickets as well 

 were caused by nutritional deficiencies, but a solid basis for general 

 belief came only after Funk's isolation of the factor preventing beri- 

 beri. 



Finally an idea of the complexity of the problem appeared when 

 McCollum and Davis (1913 to 1915) found that a combination of fac- 

 tors was required. Rats failed when fed wheat alone or wheat supple- 

 mented with a purified protein like casein, egg fat or butter, or a salt 

 mixture. Even when any three were combined rats did not grow and 

 reproduce normally. Yet they did so when all four materials were 

 used, indicating that at least four factors were essential. The inorganic 

 ions of the salt mixture and amino acids of the casein were needed to 

 supplement those of wheat. In addition, the wheat contained water- 

 soluble factors which came to be called vitamin B. The fat-soluble 

 materials, called vitamin A, came from buiter or egg. Both vitamins 

 turned oiu to be mixtures of materials. 



/Pa^/ o 77 /effu c e 



/e/fuce a77o( y?7///( 



*^ 



2C/t. 60 ^777. ' 2^f /20 ^ ??7. 



IMt / g O ^-TTl. 



FIGURE 14-1. These rats were of the same age and received the same basal diet with 

 the exception of the supplements noted. This experiment emphasizes the importance 



of milk and leafy foods in the diet. 



