232 SCIENCE PROGRESS. 



ence as regards symmetry between the products of inorganic 

 nature and organic products, the one set having a superpos- 

 able image, therefore being not dissymmetrical, the others 

 havingan image not superposable,and being therefore atomic- 

 ally dissymmetrical, " this dissymmetry expressing itself 

 externally in the power of turning the plane of polarisation ". 



In 1854 Pasteur was nominated Dean of the Faculty of 

 Sciences at Lille, and a new series of investigations was 

 commenced. 



It is curious that such a purely physical question as that 

 above outlined should be the real foundation of Pasteur's 

 contributions to the solution of some of the great biological 

 problems that at this time were occupying the minds of 

 scientific men. It was already known that impure tartrate 

 of lime contaminated with organic matter and kept in water 

 would undergo a process of fermentation during which various 

 products were yielded. In order to examine this process 

 Pasteur took about one hundred parts of the pure crystalline 

 right-handed tartrate of ammonia, dissolved it, and added to 

 the solution one part of albuminoid matter. He found that 

 when this was placed in a warm chamber fermentation took 

 place, and the clear solution became turbid, this turbidity being 

 due to the appearance of a number of minute organisms which, 

 following up the analogy of the presence of yeasts in alcoholic 

 fermentation, he assumed must be the cause of this special 

 form of fermentation. He then obtained similar fermentation 

 in a solution of paratartrate of ammonia, when he found that 

 the same organism still made its appearance. Following one 

 of the changes that took place in the fermentation of the two 

 salts with the aid of the polariscope he found that in the case of 

 the paratartrate, rotation of light to the left could be demon- 

 strated at an early age of the process, from which it was 

 evident that the right-handed tartrate only was being 

 attacked and broken down under the process of fermenta- 

 tion ; this was allowed to go on until the deviation to the 

 left had attained a maximum, " the fermentation was then 

 suspended, there was no longer any of the right-handed 

 acid in the liquid, which, when evaporated and mixed 

 with its own \olume of alcohol, immediately furnished a 



