ALBUMINS OR PROTEINS. 191 



are characteristic of the individual tissues. The secret of the individuality 

 of the various cells undoubtedly depends on their configuration. Every 

 species, every variety, in fact, every individual, has its own " albu- 

 min." According to this conception, the carbohydrates are of less sig- 

 nificance to the animal organism. They are essentially food materials, 

 and are necessarily but a small factor in the production of animal tissues. 

 It is entirely different when we consider the vegetable kingdom. The 

 carbohydrates predominate here. They construct the plant tissues, and 

 all the numerous living processes are dependent on their presence. Hence 

 their variety, and their production from the heterogeneous elements. 

 Carbohydrates, as regards their entire physiological significance and their 

 composition, are to the vegetable world what the protein substances are to 

 the animal organism. 



The greater the number of amino acids participating in the composition 

 of a protein, the wider the uses to which that protein can be put. On 

 the other hand, the simpler the function of the protein, the more dominant 

 becomes one or the other of the amino acids. Fibroin from silk, for 

 instance, contains 36 per cent glycocoll, and over 20 per cent alanine; 

 elastin gives us 26 per cent glycocoll, and over 10 per cent leucine; gliadin, 

 a " reserve albumin " of plants, contains over 30 per cent glutamic acid; 

 while in the protamines we often find over 80 per cent arginine. It would, 

 of course, be wrong to compare these albuminous bodies with others, and 

 say that they were simple in composition. They are simply more homo- 

 geneous. Whether the amino acids grouped together are all of a kind or 

 much diversified, has but little bearing on the question of their constitu- 

 tion or configuration. 



The observation that the pancreatic ferment does not attack some of 

 the synthetic polypeptides, and the discovery that during the digestion of 

 proteins many complicated cleavage-products remain, which still contain 

 large percentages of glycocoll, phenylalanine, and Z-proline, leads us to con- 

 clude that the animal organism utilizes such groups, or similar ones, as a 

 foundation, or back-bone, for building up new albuminous substances. It 

 is certainly of some significance that elastin contains so much glycocoll and 

 leucine. The combination leucyl-glycine, on the other hand, is obviously 

 unacted upon by trypsin. Silk also contains such compounds, as is shown 

 by the discovery of glycyl-d-alanine in it. The cell can protect itself by 

 forming just such combinations. The fact that most vigorous fermenta- 

 tion processes are continually taking place in the cell, and that in spite of 

 this the cell retains its own constituents its amour intact, becomes 

 much more comprehensible to us from such considerations. 



The significance of Emil Fischer's synthetic polypeptides lies, moreover, 

 in still another direction. Up to the present time it has not been possible 

 to test the proteolytic ferments as to their homogeneity. We have to 



