186 



SCIENCE 



[N. S. Vol. XXXVII. No. 944 



entire absence of tryptophane and lysine, for 

 feeding experiments with zein were expected 

 to shed light on the important question of 

 amino-acid synthesis by the animal. 



Maize glutelin, in contrast to zein, yields 

 all of the amino-acids commonly found in 

 proteins and in proportions corresponding to 

 those yielded by the majority of animal or 

 Tegetable proteins. 



The globulins, albumins, and proteoses oc- 

 cur in such small quantities that it has not 

 been possible to obtain them in sufficient 

 amount to determine their amino-acid make- 

 up, or their value in nutrition. 



and food intake, broken line, of several rats 

 fed on our protein-free milk diet.° During 

 period 2 all of these rats had a diet containing 

 zein as its sole protein and, as you will note, 

 they rapidly declined in weight, although the 

 food intake remained nearly constant, or was 

 even increased, as shown by rats 617 and 64Y. 

 That this quantity of food was sufficient for 

 maintenance is shown by rats 628 and 659, 

 which regained part of their lost weight on 

 an even smaller quantity of food after the zein 

 had been replaced by gliadin. The increased 

 food intake when zein was replaced by casein, 

 edestin or lactalbumin is largely to be ascribed 



Last fall the results of two experiments 

 with mature rats supplied with food contain- 

 ing zein as its sole protein were described. In 

 both cases the animals declined rapidly in 

 weight, although their food intake remained 

 practically constant. These results have since 

 been confirmed by a large number of experi- 

 ments, some of which are illustrated by the 

 following charts. 



Chart I. shows the body weight, solid line, 



to the rapid gain in weight which took place 

 when this change was made in the ration. It 

 might be thought that a failure to digest and 

 assimilate zein was the cause of the decline on 

 the zein diet, but curves which you will see 

 later show that can not be so, for the addition. 

 of a small amount of tryptophane renders the 



"Science, N. S., Vol. XXXIV., No. 882, pp. 

 722-733, November 24, 1911. 



