FIKST DISCOVERIES. 35 



III. 



Pasteur had thus established that bodies endowed 

 with internal dissymmetry carried this property, in 

 varying degrees, into their compounds or their deriva- 

 tives. When two of these bodies whose nature has 

 been revealed by the discovery of right-handed and 

 left-handed tartaric acid, where all is chemically iden- 

 ticaland which are only to be distinguished from 

 each other by their inverse crystallographic form, and 

 by their action on polarised light enter into combina- 

 tion with a substance which is optically and crystallo- 

 graphically inert, the chemical identity ought, under 

 these new conditions, to be preserved. Everything 

 remains optically and crystallographically comparable. 

 The inert element adds nothing to, and takes away 

 nothing from, the dissymmetric faculties of the active 

 one. 



To these curious studies Pasteur soon added a new 

 chapter. He reasoned thus : If into these compounds 

 I introduce a substance possessing in itself the specific 

 properties of dissymmetry, it is evident that this sub- 

 stance, while entering into these combinations, must 

 preserve its own properties. The active substance 

 would, from the moment of its combination, add some- 

 thing to the properties of the molecular group which 

 acts like itself, and subtract something from the 



