236 THE POPULAR SCIENCE MONTHLY. 



old gentleman was disconcerted, and declared it was his business to 

 question the pupil, not Pasteur's to question him. Pasteur then had 

 recourse to a pharmacist in the town who had gained some distinction 

 in science, and took private lessons in chemistry from him. He fared 

 better at the f^cole Normale, where he had Balard for a teacher, and 

 also enjoyed the instructions of Dumas, with whom he formed a life- 

 long friendship at the Sorbonne. 



Pasteur's first important investigation was suggested at about this 

 time, by an observation of Mitscherlich, the German mineralogist, of 

 a difference in the behavior toward polarized light of the crystals of 

 paratartrate of soda and ammonia and tartrate of soda and ammonia, 

 bodies identical in composition and external form and other proper- 

 ties. Pasteur discovered differences in the form of the crystals and 

 the molecular structure of the two bodies that had escaped detection, 

 and was led to consider that all things may be divided into two cate- 

 gories : those having a plane of symmetry — that is, capable of being 

 divided so that the parts on either side of the plane of division shall 

 be equal and identical — or symmetrical bodies ; and dissymmetrical 

 bodies, or those not capable of being so divided. Occupied with the 

 idea that symmetry or dissymmetry in the molecular arrangement 

 of any chemical substance must be manifested in all its properties ca- 

 pable of showing the quality, he pursued his investigations till he 

 reached the conclusion that an essential difference in properties as to 

 symmetry exists between mineral and dead matter and matter in 

 which life is in course of development, the former being symmetrical, 

 the latter unsymmetrical. 



Pasteur's wedding-day came on while he was engaged in this in- 

 vestigation. He went, not to the marriage-feast, but to his laboratory, 

 and had to be sent for when all was ready. 



With his observing powers quickened by his studies of symmetry 

 and dissymmetry, Pasteur went to the researches with which his life 

 has been identified, beginning with his studies in fermentation. Lie- 

 big's theory, that fermentation is a change undergone by nitrogenous 

 substances under the influence of the oxygen of the air, ruled at the 

 time, and the observations of Schwann and Cagniard-Latour on the 

 yeast-plant were overlooked or regarded as exceptional. M. Pasteur 

 continued the investigation of the alcohol-producing yeast-plant, and, 

 cultivating it in suitable solutions, proved that it possessed organiz- 

 ing power ample to account for the phenomena. He found a similar 

 organism — minute cells or articulations narrowly contracted in the 

 middle — active in the lactic fermentation, capable of cultivation ; and 

 another organism, a vibrion, full of motion, living singly or in chains, 

 working in the butyric fermentation. 



The butyric vibrion was found to work quite as vigorously and with 

 as much effect when no air was added to the decoctions, and in fact to 

 perish with a stoppage of the formation of butyric acid when air was 



