VITAMINS 



227 



in the form of its pyrophosphoric acid ester, which is known as cocar- 

 boxylase. This substance is required for the action of various enzymes 

 (for example, carboxylase and pyruvic oxidase), which function in the 

 breakdown of pyruvic acid formed during normal carbohydrate metab- 

 olism. Thus when the body is deprived of an adequate amount of thi- 

 amine, pyruvic acid accumulates in the blood, heart, and nervous tissues 

 until toxic concentrations are reached, and the visible symptoms of beri- 

 beri result. Degeneration of nerve tissue formerly attributed to a lack 

 of thiamine is apparently the result of other dietary deficiencies. Animals 

 that receive adequate amounts of vitamin A and riboflavin but an in- 

 sufficient amount of thiamine show no degeneration of nerve tissue. 



Another characteristic symptom in thiamine deficient animals is ano- 

 rexia, or loss of appetite. Administration of the vitamin to such animals 



Courtesy of the Dept. of Biochemistry, University of Wisconsin. 

 Fig. 9-5. Thiamine deficiency in the chick. The posture is typical of poly- 

 neuritis in birds. 



results in a phenomenal stimulation of the desire to eat, and the animals 

 may consume as much food in the succeeding twenty-four hours as they 

 had previously in an entire week. The growth of young animals on thi- 

 amine deficient diets is subnormal long before the severe symptoms of 

 polyneuritis become apparent. Thiamine has also been used with fair 

 success as a stimulant to the appetite in human beings. However, it 

 should be emphasized that many other factors also affect the appetite 

 and that thiamine is probably only effective in those cases where the 

 anorexia is actually due to a lack of this particular vitamin. Decreased 



