FERMENTS. 473 



Moreover, the ferments are so sensitive that they can detect differences 

 in chemical compounds which are, as far as our present knowledge of 

 structure and stereo-chemistry shows, perfectly analogous. This is clearly 

 shown by comparing the a- and /?-methyl-d-glucosides with the a- and /?- 

 methylxylosides. 



H . C^OCH 3 CH 3 O . 



H . C . OI^ H . C . GET 



l x o i r> 



HO . C . H , HO . C . H 



H . C/ H . C/ 



H . C . OH H . C . OH 



CH 2 



2 . OH CH 2 . OH 



a- and /?-methyl-d-glucosides 



H . C . OCH 3 CH 3 O . C^H 



H . C . OEt\ H . C . 



HO . C . H 



H.A. 



CH 2 . OH C 



a- and ^5-methylxylosides 



While the former are split by either emulsin or the yeast ferments, the 

 xylosides are not acted upon by either of them. 



Emil Fischer made analogous observations with the polysaccharides. 

 Some of these are also unfermentable, and their different behavior is 

 undoubtedly due to differences in the configuration of the molecules. 1 



For investigating the relations of the action of ferments to the con- 

 figuration of the individual compounds, Emil Fischer by his extensive 

 syntheses in the protein group has opened up recently a new field which 

 in its diversity far exceeds the relations with the carbohydrates. This 

 scientist has, as we have already seen, made the cleavage-products of the 

 proteins unite together in various anhydride-like combinations. The 

 number of chains which it is possible to unite in this manner is very large. 

 The number of possible isomers which can be obtained by using different 

 amino acids and in different sequence, and also by employing the racemic 

 amino acids, is greatly increased on account of the fact that all of the known 

 cleavage-products of albumin, with the exception of glycocoll, contain at 



1 Compare also A. Kalanthar : Z. physiol. Chem. 26, 89 (1898). 



