302 



sation of glycerose, formaldehyde, or acroleine-bromide, would neces- 

 sarily lead to all sixteen possible isomeric aldoses and all the eight 

 ketoses. Instead of this, besides x-acrose, only a single racemic hexose 

 is obtained ; and this clearly proves that there is a certain preferential 

 direction in the synthesis of these sugars under these conditions. 

 The same must be the case in the important cyanohydrine-rezction ; 

 when a certain dissymmetry of the reacting molecule pre-exists, 

 the addition of HCN no longer occurs in a symmetrical way. Thus, 

 in using man-nose, the one antipode of mannoheptonic acid l ) was 

 obtained to an amount of 87%, whereas of the other no appreciable 

 quantity was found. 



With this evidence Fischer undoubtedly for the first time 

 brought clearly to the fore the essential features of "asymmetric" 

 synthesis in general. Natural synthesis in the living organism 

 takes place in a one-sided way, because it occurs under collaboration 

 of optically active molecules; the dissymmetrical arrangement of 

 such molecules taking part in the chemical processes has a guiding 

 influence, and thus a single optically active compound of a whole 

 set of isomerides is formed in greater quantity than the others. 



However, it would perhaps be preferable to draw attention 

 more particularly to the differences in speed 2 ) in the process of 

 synthesis of the isomeric substances. For the possibility of life- 

 processes is at bottom, - - from a chemical point of view, --a 

 question of the mutual regulation of reaction- velocities : the orga- 

 nism cannot stop its physiological functions for a single moment. 

 It produces and consumes continually, and these processes of 

 synthesis and metabolism, of waste and production, must all go 

 on with definite, well regulated mutual velocities, if the life- 

 process is to be carried on. at all. A state of completed "reaction- 

 equilibrium" is never, therefore, reached: only a kind of apparent 

 "dynamical constancy". Now it is most probable that other iso- 

 merides than those found in the vegetable cells, are formed 

 simultaneously in the synthetic process, but at an incomparably 

 smaller rate. It is possible, that there are exceedingly small 



!) E. Fischer, Ber. d. d. Chem. Ges., 22, 370, (1889). 



2 ) Erlenmeyer's hypothesis of "asymmetrical induction" (Bioch. Zeits., 97, 

 198, 231, 244, (1919)) for the explanation of partially asymmetrical synthesis, is 

 by no means contradictory to the views here exposed about the difference of 

 velocity of the possible reactions to be considered in such cases; in fact both ways 

 of explanation are wholly compatible with each other; cf. : loco cit., p. 241, etc. 



