144 PHYSIOLOGY OF THE BACTERIA. 



this subject. Let us, however, mention before 

 closing an interesting work by MM. Cazeneuve 

 and Livon, in which are reported some experiments 

 which prove that urine never ferments in a healthy 

 bladder. 



Lactic, Butyric, and Viscous Fermentations of 

 Sugars. — Saccharine liquids, left to themselves, 

 are susceptible of divers fermentations, which may 

 occur separately or simultaneously. Those which 

 have been best studied are three, — the lactic, the 

 butyric, and the viscous fermentations. We will 

 describe them successively. 



1. Lactic Fermentation. — Under the probable 

 influence of a bacterium {ferment lactique of Pas- 

 teur) glucose and the substances susceptible of 

 furnishing it, such as mannite, malic acid, etc., are 

 transformed into lactic acid. 



From a chemical point of view, there is in this 

 nothing more than a molecular change, lactic acid 

 having the same composition as glucose. 



Taken in mass, the lactic ferment resembles 

 beer-yeast ; its consistence is, however, a little more 

 viscous, and its color more gray. But under the 

 microscope, the aspect is very different, as we have 

 seen in describing Bacterium lineola. 



An interesting point concerning this fermenta- 

 tion is the action of acids upon the bacteria which 

 produce it (presumably). As soon as the medium 

 becomes acid, even by the lactic acid produced, the 

 transformation is arrested. It resumes its course, 

 if chalk or carbonate of soda is added to the 

 liquid. 



