30 LOUIS PASTEUR 



an important leavo rotation. Then the excited man 

 seized my hand and said, 'My dear child, I have 

 all my life so loved this science that I can hear my 

 heart beat for joy.' " This seance was the begin- 

 ning of a friendship between the old man of science 

 and the younger one that lasted throughout the 

 former's life. 



The relation between crystalline form and ro- 

 tary power discovered in the tartrates Pasteur was 

 eager to test upon other materials in order to ascer- 

 tain how generally this relationship might be found 

 to occur. It was not easy to find many forms with 

 asymmetrical crystals which proved at the same 

 time to have the power of turning the plane of 

 polarized light. Asparagin proved to be one of 

 these, and was found to have the peculiar power 

 of rotating the plane of polarization to the left in 

 alkaline or neutral solutions, but to the right in 

 acid solutions. Malic acid and its salts were found 

 to have both right-handed and left-handed crystals, 

 whose action on light was frequently the same as 

 that of the tartrates, but it sometimes behaved in 

 an apparently contradictory manner that Pasteur 

 was unable to explain. It is now known that in 

 dealing with the salts of aspartic and malic acids, 

 Pasteur fell into certain errors of detail, which pre- 



