132 BACTERIA. 



connection with the production of specific infective diseases 

 in man and animals by micro-organisms. 



There has, indeed, been so much work to be done in 

 separating out the causal bacterial agents in these diseases, 

 that there has been little time or energy left to be devoted 

 to anything more than a most cursory study of the 

 chemical and biological processes of the non-pathogenic 

 forms. We do know, however, something about the man- 

 nitic fermentation of sugar, the lactic, the butyric, the 

 ammoniacal, and the acetic fermentation ; and, speaking 

 generally, these processes are essentially the same as those 

 which take place in ordinary alcoholic fermentation, the 

 differences being that the protoplasm cells of the ferment 

 differ from those of yeast both in morphological and bio- 

 logical characteristics, and that the composition of the 

 end - products is also different. The food material acted 

 upon by different protoplasm, and giving rise to different 

 results, may be the same ; the fermentation is still brought 

 about by a process of hydration or some other specific 

 process, and is intimately associated with the vital activity 

 of the special ferment. In the mannitic fermentation 

 the sugar is converted by hydration into dextrose and 

 levulose, after which comes the conversion of some of the 

 sugar into gum, and of some into mannite, during which 

 second part of the process there is also an evolution of carbon 

 dioxide and the formation of water. Mannite is a sugar to 

 which a molecule of hydrogen has been added ; gum, a 

 cane sugar from which one molecule of water has been sub- 

 tracted. The viscous change that takes place as the fermen- 

 tation proceeds is due to the formation of this gummy 

 material in the fluid. Pasteur described the special man- 

 nitic ferment as consisting of chains of small cocci, each 

 coccus having a diameter of 1.2 to i.$fi of an inch. 

 These, like the yeasts, require nitrogenous material, in 

 addition to salts, extractives, and sugar, in order that they 

 rriay develop. This form of fermentation is specially in- 

 teresting, from the fact that it is to it that the ropiness of 

 the white wines is due — a ropiness which, as Pasteur pointed 

 out, might be prevented by heating the wine for a few 

 minutes at a temperature of 60° C, or, as suggested by 

 Frangois, by the addition of a certain proportion of tannin, a 

 substance which appears to interfere most markedly with 

 the development of the viscous fermentation organism. 



