28 PASTEUR : THE HISTORY OF A MIND 



VII 



DISSYMMETRY OF CELLULAR LIFE 



The plant, which is the great creator of organic matter 

 on the surface of the globe, is an organism continually 

 engaged in the work of synthesis. By the aid of sub- 

 stances of the highest degree of chemical simplicity, 

 carbonic acid, water and ammonia, it manufactures sub- 

 stances more and more complex, which it stores in the 

 new tissues that it forms according to its needs. As 

 soon as these substances attain a certain degree of com- 

 plexity we see appearing in them the molecular rotary 

 power, absent up to that time. Carbonic acid, oxalic 

 acid, acetic acid, ammonia, urea and glycocol, are with- 

 out action on polarized light: the sugars, tartaric, malic 

 and citric acids, cellulose, the gums, and the albuminoid 

 substances are active. 



At the time when Pasteur made these studies the chem- 

 istry of synthesis was still little advanced: Berthelot was 

 just beginning his work. But organic chemistry was in 

 full swing, and inorganic chemistry was leaving the 

 hands of Berzelius and Wohler to fall into those of 

 Sainte-Claire Deville. Already, at this time, Pasteur 

 was in position to remark that, contrary to the majority 

 of natural organic products, all the artificial products 

 of the laboratories and all the mineral species met with 

 in nature were without action on polarized light, that is 

 to say, they possessed a superposable image. (Quartz 

 itself is not an exception, for, as we have seen, it is only 

 the arrangement of the molecules in the crystal which is 

 dissymmetrical. Individually these molecules are with- 

 out action on polarized light. In the same way one can 

 arrange cubes of wood, which are exactly alike, so as to 

 make a winding and dissymmetrical staircase; there 



