42 PASTEUR: THE HISTORY OF A MIND 



It is true that this is not always the case, and Pasteur 

 would have been able to find contrary examples in the 

 history of the malates if he had not made the error which 

 we have pointed out above. But, on the whole, one 

 can accept this way of looking at it as sufficiently ex- 

 act, and Pasteur was right to introduce it into science. 

 The marked differences which one observes between the 

 various sugars encountered in nature, for example be- 

 tween rock candy and its constituent sugars, are evidently 

 of the same order and have the same origin. I will ven- 

 tiu-e to add that it is reasons of the same kind which render 

 so baffling the study of albuminoid substances, in which 

 differences of molecular structure are expressed exter- 

 nally otherwise than by differences in crystallization. 



If w^e now recall that the protoplasm of all living 

 cells is endowed \\dth the rotary power, that it con- 

 tains, therefore, dissymmetrical molecules, and that 

 this dissymmetry in relation to the stability or insta- 

 biUty of the compound, cannot fail to play a role in all 

 the chemical combinations of which the protoplasm is 

 the seat, we shall conclude that there are in these con- 

 siderations indications of a profound mechanism of life. 

 We encounter here one of those flights of imagination 

 which Pasteur permitted himself sometimes and which 

 were for him the recompense and the repose derived 

 from works of research. But when he had thus boldly 

 explored the horizon he made haste to regain the solid 

 ground of experiment. Let us follow his example and 

 enter the laboratory. 



