FIRST DISCOVERIES. 33 



who later on became one of the correspondents of the 

 Academy of Sciences, announced that he had trans- 

 formed fumaric and malic acids into aspartic acid. 

 Pasteur, who some time previously had had occasion 

 to study these same acids, had proved that the two 

 first had no molecular dissymmetry that is to say, 

 they exercised no optic action. In the state of so- 

 lution they did not turn the plane of polarised light. 

 Aspartic acid, on the contrary, had presented to him 

 molecular dissymmetry, like asparagine itself. If the 

 observation of M. Dessaignes were true, then bodies 

 which were inert in regard to polarised light, and con- 

 sequently non-dissymmetric, could be transformed in 

 the laboratory into active dissymmetric bodies. The 

 line of demarcation so well established would be broken. 

 Pasteur, whose experience regarding the note of 

 Mitscherlich had shown him how even the most con- 

 scientious observers may fail to seize upon fugitive 

 appearances, when unprompted to seek them by a 

 preconceived idea, doubted at once the accuracy of the 

 facts cited by M. Dessaignes. From Strasburg he 

 started for Vendome, where M. Dessaignes at that time 

 resided. M. Dessaignes immediately gave Pasteur a 

 small quantity of the aspartic acid which he had pre- 

 pared by means of fumaric and malic acids. Keturn- 

 ing to his laboratory, Pasteur immediately recognised 

 that, despite the very close resemblance of the new acid 

 of M. Dessaignes to that derived from asparagine, 



