ARTHUR ISAAC KENDALL 



235 



much attention was paid to this observation until Fischer, the master-chemist of 

 the carbohydrates, and his pupil, Thierf elder,' exposed various members of the hexose 

 series of sugars to the action of yeasts. They found at once that certain members of 

 the glucose series, always with the ^/-configuration, were consistently fermented by 

 yeast, whereas other members were equally consistently left unattacked. Fischer 

 grasped the meaning of this remarkable relationship between carbohydrate configura- 

 tion and the ability of the yeast to utilize certain configurations as a very fundamental 

 biological phenomenon. His famous simile of the "key and the lock" is ample 

 evidence of his comprehension of the significance of this very important phenomenon. 

 He states: "Bei dieser Annahme ware es nicht schwer zu verstehen, dass die Hefezel- 

 len mit ihrem asymmetrisch geformenten Agens nur in die Zuckerarten eingreifen 

 und garungserregend wirken konnen, deren Geometric nicht zu weit von derjenigen 

 des Traubenzuckers abweicht."^ Fischer and Thierf elder also showed that all the 

 yeasts they studied fermented all those hexoses of the glucose series that had a com- 

 mon enol — namely, glucose, mannose, and fructose. That is to say, their experiments 

 showed very clearly that a yeast culture which fermented any one of these three 

 hexoses fermented the others as well. Armstrong^ has reaffirmed this conclusion. 



Bacteria are considerably more versatile in their fermentation reactions in the 

 aggregate than yeasts, and it is to be deplored that bacteriology had not developed 

 far enough when Fischer was studying this profoundly interesting "biochemical 

 geometry" to provide him with some of the more active fermenting types to extend 

 this highly important field. 



It is now well known that several important groups of bacteria, e.g., members of 

 the Bacillus proteus and Vibrio comma group, do not ferment mannose-i at all, 

 and several other similar instances are known. Furthermore, such changes of terminal 

 groups in the glucose molecule as are shown below alter the utilization of the resulting 

 compound for many bacteria, thus:^ 



H 



' Fischer, E.: loc. at.; Thierfelder, H.: loc. cit. ' Fischer, E.: loc. cit. 



3 Armstrong, E. F.: op. cit., p. 171. 1924. 



'• Kendall, A. I., and Yoshida, S.: /. Infect. Dis., 32, 355. 1923. 



s For convenience the older formula for glucose is used in place of the closed-chain formula, and 

 the acids are not written in the lactone form. 



