1903.] on Becent Advances in Stereochemistry. 315 



in the molecule, with about equal facility ; d-galactose is, however, 

 only fermented with difficulty — of its four asymmetric carbon atoms, 

 one differs in configuration from the corresponding one in the easily 

 fermentable d-glucose ; d-talose, in which two of the asymmetric 

 carbon atoms differ in configuration from the corresponding atoms in 

 d-glucoso; is quite unaffected by the yeast. It is just as if the enzyme 

 were provided with hands which enable it to grip the sugar mole- 

 cule before tearing it to pieces ; with these hands it grips the corre- 

 sponding hands of, and so obtains a firm hold upon, the molecules of 

 the first three sugars. The enzyme can only, however, grip the 

 d-galactose molecule by two hands and so obtains a less firm hold. 

 Owing to the greater incompatibility between the zymase and the 

 d-talose the former obtains too feeble a hold on the latter to enable 

 it to make a successful assault, and the sugar therefore remains 

 unfermented. 



The fact that the chemical reactions of animal and vegetable 

 physiology consist in the main, of the production or destruction of 

 optically active substances through the agency of enantiomorphous 

 enzymes, is one of enormous importance. The complex substances 

 concerned, such as starches, albumins and food-stuffs generally, occur 

 in nature in but one of the enantiomorphously related configurations ; 

 all the albumins are laevo-rotatory, all the starches and sugars are 

 derived from dextro-glucose. Since Fischer's work teaches us that 

 none of the sugars derived from laevo-glucose are fermentable by 

 yeast, it would seem to follow as a legitimate conclusion that, whilst 

 d-glucose is a valuable food-stuff,iwe should be incapable of digesting 

 its enantiomorphously related isomeride, 1- glucose. Humanity is 

 therefore composed of dextro-men and dextro- women. And just as 

 we ourselves would probably starve if provided with nothing but food 

 enantiomorphously related to that to which we are accustomed, so, if 

 our enantiomorphously related isomerides, the Isevo-men, were to 

 come among us now, at a time when we have not yet succeeded in 

 preparing synthetically the more important food-stuffs, we should be 

 unable to provide them with the food necessary to keep them alive. 



[W. J. P.] 



