217 



by a number of chemists, directly to produce an optically ; 

 Mibst.m. v I nun an inactive material by mere chemical action. In 

 tin- next chapter we shall return to these interesting and fundamental 

 <|ur>tions in detail; it suffices here to point out the fact that i;ui(lrd 

 by this preconceived idea, Pasteur started to investigate more 

 accurately the action of various moulds on solutions of calcium- 

 and ammonium-racemates, after he had accidentally observed that 

 these can grow in them. He tried to answer the question, as to what 

 would be the behaviour of the two components of the racemate 

 under the influence of the living organism. 



He found that the originally inactive solution became gradually 

 laevogymtory ; the organism (Penicillium glaucum) had evidently 

 selected for its nutriment that form of the tartaric aW-molecule 

 \\lrn h suited best its particular needs. Although this selective con- 

 sumption of one of the antipodes by living organisms has been often 

 found, it must however be recognised that the selective fermen- 

 tations as a general phenomenon, have not yet been studied in a 

 sufficiently systematic way *). In numerous cases we do not know 

 whether the culture used was of only one species, nor to what species 

 the organisms belonged in many cases. Neither is there certainty 

 as to whether the organism merely decomposes one active component 

 of the mixture more rapidly than the other, or whether it leaves one 

 of them entirely intact. Most probably there is only a great difference 

 of rate of velocity. 



It may be thought most remarkable, that such a relatively minute 

 difference between two molecules should be sufficient to cause such 

 a fundamental difference in the behaviour of a living organism if 

 brought into contact with it. More recent experiments however have 

 not only proved this fact beyond all doubt, but from E. Fischer's 

 work 2 ) on the selective fermentation of sugars under the action 

 of yeasts, it seems probable that the action of every living organism 

 corresponds to only a definite, very exclusive, special arrangement 

 of the atoms in the chemical molecules. 



However in recent times serious doubt has .arisen, as to whether 

 the specificity of the action of organisms, as brought to the fore 

 by Fischer, and illustrated by his image of lock and key, should 



1) As an interesting contribution however, see: W. Pfeffer, Jahrb. f. wiss. 

 Botanik, 28. 205. (1892). 



2) E. Fischer and collaborators, Ber. d. d. Chem. Ges. 27. 2031, 2985, 3228, 

 3479. (1894); 28. 1429, 1508, 3031. (1895); Zeits. f. physiol. Chemie 26. 60. (1898). 





