36 PASTEUR: THE HISTORY OF A MIND 



of a relation, not only between the existence of a rotary 

 power and a dissymmetry of construction in the quartz 

 crystal, but also between the direction of this power and 

 that of this dissymmetry. Biot shows us subsequently 

 that the rotary power can exist in the molecule. Where- 

 from Pasteur concludes that there must be a dissymmetry 

 in the construction of the molecule, that is to say in the 

 arrangement of the atoms. He finds the external indica- 

 tion of this dissymmetry in the tartrates, which serve him, 

 furthermore, to state precisely the meaning of this word 

 dissymmetry, up to that time a little vague. In his 

 mind, then, after his studies on the aspartates and 

 malates, these tartrates become, as did the quartz, 

 merely empty shells, after yielding the idea which 

 they contained. This idea is that of the dissymmetry of 

 the molecular structure and of its constant relation to 

 the rotary power. 



There we have the portion of truth which this memoir 

 contains! On reflection the conclusion to which we 

 arrive will appear curious from the philosophical point of 

 view, for here we have a work which had begun by estab- 

 lishing a close relation between the rotary power and the 

 crystalline form, and which ends by scorning this crystal- 

 line form. One might think that science had turned 

 about in its place without advancing. But he would be 

 deceived, for here we see clearly how much a matter of 

 indifference it is whether a theory or a doctrine is right, 

 provided that it incites to work, and results in the dis- 

 covery of new facts. We do not know exactly what is 

 the relation between the molecular structure and the 

 crystalline form, nor even if there is a relation which 

 makes it necessary that they should be subject one to 

 the other. Fundamentally a correlation between the 

 existence of certain crystalline facets and the arrange- 

 ments of atoms in the molecule, appears to us rather 



