FERMENTATION. 51 



motion, which up to that time had reigned in science, 

 were completely overthrown. 



II. 



The light shed by these experiments quickly ex- 

 tended its sphere ; and Pasteur lost no time in dis- 

 covering a new ferment, that of butyric acid. Having 

 shown the absolute independence which exists between 

 the ferment of butyric acid and the others, he found, 

 contrary to the general belief, that the lactic ferment is 

 incapable of giving rise to butyric acid, and that there 

 exists a butyric fermentation having its own special 

 ferment. This ferment consists of a species of vibrio. 

 Little transparent cylindrical rods, rounded at their ex- 

 tremities, isolated or united in chains of two or three, or 

 sometimes even more, form these vibrios. They move by 

 gliding, the body straight, or bending and undulating. 

 They reproduce themselves by fission, and to this mode 

 of generation their frequent arrangement in the form 

 of a chain is due. 



Sometimes one of the little rods, with a train of 

 others behind it, agitates itself in a lively manner as if 

 to detach itself from the rest. Often, also, the little 

 rod, after being broken off, holds on still to its chain 

 by a mucous transparent thread. 



These little infusorise may be sown like the yeast 

 of beer or the lactic ferment. If the medium in 



