ALBUMINS OR PROTEINS. 187 



in the absence of proteolytic action, a second polypeptide could be obtained 

 in the form of its anhydride; namely, glycyl-/-tyrosine and Z-tyrosyl- 

 glycine. Finally it has been found possible to isolate from elastin, 

 glycyl-Z-leucine anhydride 1 and d-alanyl-leucine anhydride; 2 furthermore, 

 glycyl-d-alanine has been isolated directly from silk, 2 and /-leucyl-d- 

 glutamic acid prepared from gliadin. 2 The most important discovery in 

 this field is undoubtedly the fact that the tetrapeptide 2 obtained from 

 silk-fibroin, consisting of two glycine molecules, one of alanine, and one of 

 tyrosine, shows properties with which many albumoses correspond. This 

 proves that the albumoses are not closely related to the proteins; i.e., 

 they are not very complicated compounds. In fact, the properties of the 

 so-called albumoses result from the nature of the amino acids of which 

 they are composed. In the above case the properties of Z-tyrosine are 

 evident. It will be well, in the future, to drop the name albumose, and 

 for the present speak only of peptones which are precipitated by 

 ammonium sulphate and of those which are not. The more complicated 

 cleavage-products are not precipitated by ammonium sulphate, while 

 the ] simpler ones, | e.g. tyrosine ' or cystine, are salted out by this 

 reagent. 



There is no doubt that other dipeptides, and especially those with longer 

 amino acid chains, will shortly be discovered in the same manner. The 

 train of thought suggested by Emil Fischer's difficult researches concern- 

 ing the constitution of the albumins has thereby received complete jus- 

 tification. Where formerly all was darkness, a bright light has suddenly 

 appeared. It is no longer difficult to picture the whole subject of albumin 

 decomposition. A whole array of new problems is immediately suggested 

 by Fischer's investigations. While his successes in developing the chem- 

 istry of carbohydrates and purines were of tremendous value in advancing 

 both fields from a biological standpoint, it is doubtless true that his new 

 efforts, which are of far greater biological importance, will result in great 

 changes concerning our conceptions of the entire biology of the proteins. 

 Much darkness, however, still surrounds many questions. 



We are still incapable of interpreting the significance of the albumins as 

 food .for the animal organism. We anxiously await the moment when 

 the fetters will be loosened, which for decades have restricted the progress 

 of the whole subject of biology. We are deeply interested in all problems 

 in connection with albumin. Here stands a large group of ferments 

 conceptions with no tangible support. The same applies to the tremen- 

 dous number of toxins, anti-toxins, and allied substances. All investiga- 

 tors of these various subjects are anxiously awaiting the solution of the 



1 E. Abderhalden and F. Samuely: Z. physiol. Chem. 47 (1906). 



2 E. Fischer and E. Abderhalden: Ber. 39, 752 (1906). 



