SOME NEW VIEW POINTS IN NUTRITION 397 



per cent., is of unknown composition. It is not unaltered protein, of 

 that we can be sure, because all protein is destroyed in the hydrolysis. 

 It is presumably composed of small fragments of some kind, not yet 

 recognized by chemists. The next most noticeable feature is that no 

 two of these proteins are alike in their chemical make-up. Proteins 

 from the same grain are distinctly unlike ; gliadin of wheat contains no 

 lysine, while leucosin from the same kernel contains 2.75 per cent, of 

 this basic substance; gliadin likewise contains 37 per cent, of gluta- 

 minic acid, while leucosin has less than 7 per cent. ; gliadin shows 5.6 

 per cent, of leucine, and leucosin twice that amount; gliadin contains 

 no glycocoll, while leucosin has nearly 1 per cent, of this amino-acid. 

 Such marked differences in chemical composition speak plainly regard- 

 ing the individuality of proteins, even of those which are associated 

 in the same seed. Comparison of casein from cow's milk, as a typical 

 animal product, with any of the vegetable proteins, brings to light 

 equally strong points of difference, while in gelatin we see many of the 

 familiar amino-acids reduced to a minimum or entirely lacking. While 

 it is undoubtedly true that all proteins possess certain features in com- 

 mon, it is becoming strikingly manifest that they are more or less 

 divergent in chemical constitution. It has been the custom of physi- 

 ologists in the past to lay stress upon the general rule that proteins are 

 substances capable of meeting the physiological necessities of the body 

 and that their nitrogen exists in a form suited to the needs of the 

 organism. We have been accustomed to point to gelatin as the one 

 exception to the rule, and have classed it as a protein-like substance, 

 with as much nitrogen or even more than most proteins, but not truly 

 a protein, since it can not support life. I fancy, however, that many 

 true proteins may prove, when taken alone, unable to support life. As 

 a matter of fact, few isolated proteins have been tested in this respect. 

 Most of our feeding experiments have been made with mixtures of 

 proteins, and consequently a considerable variety of protein cleavage 

 products have been available for nutritive purposes. Take, as an illus- 

 tration, the zein of corn meal, which contains no tryptophane, glycocoll 

 nor lysine whatever, and only 1.5 per cent, of arginine and histidine 

 combined, but with 18.6 per cent, of leucine, to say nothing of other 

 peculiarities of chemical structure. Is it not reasonable to suppose 

 that such a protein, with so many of the ordinary chemical groups 

 missing or in greatly diminished quantity, will prove inadequate to 

 meet the demands of protein synthesis? Experiment with animals 

 has, indeed, shown this to be the case. 



Data along these lines are bound to bring us more definite informa- 

 tion than we at present possess regarding the real merits of vege- 

 tarianism as contrasted with the use of animal foods. At present, 

 so-called vegetarianism rests mainly upon sentiment, reinforced by the 



