38 PASTEUR: THE HISTORY OF A MIND 



in the grouping of its atoms an arrangement with a super- 

 posable image. Thus each dissymmetrical substance 

 offers four variations or, rather, four distinct sub-species: 

 the right-handed body, the left-handed body, the com- 

 bination of the right and the left, and the body which is 

 neither right nor left, nor formed by a combination of the 

 two." 1 



I shall dwell no longer on the aspartic and malic acids 

 because, as I have just said, Pasteur had taken the wrong 

 route. This has been evident since, and it is singular 

 that its discovery has required no new methods; it has 

 only been necessary to employ those methods with which 

 he has made us familiar. By following them M. Bremer 

 has shown that the inactive malic acid of Pasteur was in 

 reality a paratartaric acid, that is to say, a combination 

 of right- and left-handed acids. It has been discovered 

 also that there are three asparagins, three aspartic acids, 

 three malic acids, and that the maleic acid and fumaric 

 acid are more distinct than Pasteur believed them, and 

 possess a new dissymmetry which is not expressed by 

 the appearance of a rotary power. In short, our knowl- 

 edge has been very much extended since Pasteur did his 

 work, but there has been no change in its source, and in 

 its immense development it remains faithful to this parent 

 idea of Pasteur, that all difference in the grouping of the 

 atoms of a molecule must be expressed externally in some 

 way. That Pasteur was sometimes self-deceived, and 

 that there are some defective stones in the foundation 

 which he has given to the edifice, is of no importance. 

 The essential thing is that the edifice rises without 

 crumbling, and that it does rise. 



1 De la dissymetrie moleculaire des produits organiques naturels. 

 Legon professee devant la Soci6te chimique. 1860. 



