44 PASTEUR: THE HISTORY OF A MIND 



first time he was no less happy than when he saw the 

 double paratartrate of soda and ammonia break up 

 unexpectedly. That was an unforeseen discovery on his 

 pathway; here, on the other hand, the discovery was 

 searched for and foreseen, which doubled the interest of 

 it. The paratartrate of cinchonine is not, moreover, 

 the only one which lends itself to such a separation: 

 that of quinicine is similar, but in this case it is the right- 

 handed tartrate which is deposited first. 



We are, then, in possession of a second means of 

 separating the active components of a paratartaric acid. 

 Let us say immediately that it is by this method that 

 M. Bremer demonstrated the inactive malic acid of 

 Pasteur to be in reality a combination of the right- and 

 the left-handed acids. Let us say, also, that a third 

 means was conceived by M. Gernez in the laboratory 

 of Pasteur. It was incident to the preceding in that the 

 separate crystallization of the two tartrates was provoked, 

 not by differences in solubility, but by a suitable crystal- 

 line decoy introduced into the supersaturated solution. 

 With a decoy formed of right-handed tartrate one ob- 

 tained the crystallization of the right-handed tartrate; 

 with one of the left-handed tartrate, that of the left 

 tartrate. This was, then, under another form, it is true, 

 a dissymmetrical influence introduced to obtain the 

 separation. 



Another means discovered by Pasteur is still more 

 curious and introduces us into the realm of life. It had 

 been known for a long time that lime tartrate left to 

 itself under water decomposes with the formation of 

 various products. One day Pasteur observed a solution 

 of right tartrate of ammonia placed in a flask in the 

 laboratory to be decomposing in the same way. The 

 liquid which was at first clear (let us keep this fact in 

 mind because we shall need it later) became clouded 



