ALBUMINS OR PROTEINS. 165 



Thus we speak of globuloses, vitelloses, etc. Undoubtedly, we shall even- 

 tually find that a great deal of this difference in behavior is due to the 

 different amino acids, which are contained in the different proteins, and 

 their arrangement in the molecule, so that before long we shall be able to 

 replace this purely biological conception by a chemical one. For the present 

 the investigations have gone beyond our actual knowledge, and have led to 

 certain results, which do not yet rest upon a firm foundation. For this 

 reason we shall not attempt to describe any of the numerous special albu- 

 moses and peptones, but simply content ourselves with the conception 

 itself. The albumoses are in general characterized by the fact that they 

 are precipitated when their solutions are saturated with ammonium sul- 

 phate, while the peptones then remain in solution. By means of the 

 behavior of a digesting mixture towards ammonium sulphate, we can 

 determine how far the digestion has already gone. 1 



Up to this point the changes produced upon the protein molecule by 

 the pepsin-hydrochloric acid of the stomach and the trypsin of the pan- 

 creas are apparently quite similar. In both cases albumoses and pep- 

 tones are formed. Of course the action of pepsin may nevertheless be 

 entirely different from that of trypsin in spite of this external similarity. 

 It may be that a different place in the protein molecule is attacked. 

 Unquestionably even 1 in gastric digestion a large quantity of products 

 are obtained which represent lower products than the peptones, and 

 some of these do not even give the biuret reaction. Simple amino acids, 

 however, with the exception of traces of tyrosine, have not been found 

 here. 2 



Tryptic digestion goes much farther. We quickly observe crystalline 

 depositions on the walls of the vessel in which the digestive mixture is 

 placed. This is tyrosine, which separates on account of its difficult solu- 

 bility. It is very quickly split off from the albumin molecule. In 48 

 hours, and even in less time, the entire tyrosine content of the albumin can 

 be isolated as such. 3 In the digestion of edestin from cotton-seeds, for 

 example, the following observations were made: 4 



PERCENTAGE OF TYROSINE OF THE TOTAL AMOUNT OCCURRING 



IN EDESTIN. 



1 See page 188. 



* Emil Abderhalden and Otto Rostoski: Z. physiol. Chem. 44, 265 (1905). 

 8 E. Abderhalden and B. Reinbold: Z. physiol. Chem. 44, 284 (1905). 



* Ibid. 46, 159 (1905). 



