EFFECT OF DEFICIENCY IN MAN 



frequent amongst maize-eating than among rice-eating or wheat- 

 eating communities. 2 Moreover, nicotinic acid is no less available in 

 maize than in rice, since monkeys fed on a whole maize diet accumu- 

 lated larger amounts of nicotinic acid in the liver, muscle and brain 

 than monkeys fed on milled rice ; ^ and whole wheat resulted in a 

 higher nicotinic acid content than either maize or rice. 



P. Handler * suggested that maize may be responsible for the 

 dehydration and haemo-concentration generally present in black- 

 tongue and pellagra. It has also been suggested ^ that maize does not 

 favour the growth of intestinal bacteria capable of synthesising nico- 

 tinic acid (page 268), whereas other cereals and pellagra-preventive 

 foodstuffs such as milk, which are very deficient in nicotinic acid, are 

 able to stimulate the growth of the right type of intestinal flora, 

 leading to the formation of nicotinic acid in the intestine. 



A different hypothesis was suggested by D. W. Woolley,^ who was 

 able to produce symptoms of pellagra in rats and mice by feeding a 

 chloroform extract of maize ; the condition was prevented or cured 

 by administration of nicotinamide. He therefore postulated that 

 maize contained a toxic factor responsible for its pellagragenic activity. 

 This hypothesis was supported by Kodicek et al.,"^ who found that 

 indole-3-acetic acid, which is present in maize in substantial amounts, 

 depressed the growth of rats fed a diet poor in protein, although 

 Woolley ^ considered that the toxic factor in maize was a basic sub- 

 stance. Kodicek et al.,^ however, showed that maize, after extraction 

 with aqueous acetone to remove indole-3-acetic acid, promoted a 

 growth rate significantly higher than that obtained with the un- 

 extracted maize but that when indole-3-acetic acid was added to the 

 extracted maize diet, it did not cause any retardation of growth. It 

 therefore appeared unlikely that indole-3-acetic acid was responsible, 

 as had been suggested, for the pellagragenic activity of maize. The 

 variable results obtained in these experiments with rats was attributed 

 to synthesis or destruction of nicotinic acid by the intestinal flora, the 

 activity of which was affected by indole-3-acetic acid. 



The true explanation of the pellagragenic effect of maize was 

 discovered by Krehl et al.,^ who found that the reduced growth rate 

 of rats induced by the addition of corn or corn grits to a diet low in 

 nicotinic acid could be brought back to normal by the addition of 

 either i mg. of nicotinic acid or 50 mg. of L-tryptophan per 100 g. of 

 diet. Other cereals which contained substantial amounts of trypto- 

 phan did not produce nicotinic acid deficiency in rats, so that the 

 pellagragenic activity of maize must be due to its low content of 

 tryptophan. The effect of maize could in fact be simulated by adding 

 a tryptophan-free protein or an acid-hydrolysed protein to the diet. 

 This observation explained the curious paradox, which had puzzled 

 16 241 



