298 



was founded; and it is this difference in the velocity of forma- 

 tion, as a consequence of the directing power of a pre-existing 

 dissymmetry, which doubtless gives the explanation of the apparent 

 difference between artificial and natural synthesis, with which we 

 shall now have to deal somewhat more in detail. 



Indeed, in the preceding chapter we have had occasion to see, 

 how in the laboratory optically active substances can only be 

 obtained from inactive materials, if one of the special methods 

 of fission proposed by Pasteur is suitably applied. If in artificial 

 synthesis we start with optically inactive materials, we only can 

 get optically inactive compounds, even when a new asymmetrical 

 carbon-atom is produced in the molecule under investigation. 



Our synthetic products are always racemic substances or exter- 

 nally compensated mixtures; and the explanation of this has 

 always been given by drawing attention to the fact that in 

 reactions, in which only symmetrical causes play a role, enantio- 

 morphously related molecules must have the same mechanical 

 stability. This very assumption has been the principle which led 

 to the discovery of our usual fission-methods by Pasteur. 



It must, however, be clear on closer examination that, properly 

 speaking, in these niethods of fission we in the end always make 

 use of the phenomena of life, as manifested in the chemical syn- 

 thesis which occurs in the cells of animals and plants. If we leave 

 the method of fission by spontaneous crystallisation aside for the 

 moment, we can only use for our purpose: either the combination 

 of racemoids with the optically active acids or bases which are 

 isolated from plants or animals; or we make use of the apparently 

 selective action of ferments and enzymes, which also are only pro- 

 duced by living cells. 



The living plant or animal, in striking contrast to what we 

 observe in our laboratory-experiments, seems to produce directly 

 from inactive materials such as carbon-dioxide, water, ammonia, 

 hydrocyanic acid, etc., the optically active substances which are met 

 with in its organism, unaccompanied by their optical antipodes. 



The majority of proteids are laevogyratory, the bile-acids dextro- 

 gyratory. Plants always produce the same optically active coniine, 

 nicotine, strychnine, etc., and the quantitative experiments of 

 Brown and Morris J ) on the formation of the carbohydrates 



H. T. Brown and G. H. Morris, Journ. Chem. Soc. London, 63, 604, (1893). 



