136 PHYSIOLOGY OF THE BACTERIA. 



CHAPTER II. 



DEVELOPMENT OF THE BACTERIA IN 

 DIFFERENT MEDIA. 



IN studying the conditions of life and of develop- 

 ment of bacteria in the different media, natural 

 and artificial, in which they are met, we will con- 

 sider the actions which they determine (or that 

 they accompany) as particular cases of their nutri- 

 tion and of their reproduction. We will con- 

 stantly take, then, their normal physiology as our 

 point of departure ; and we will try to explain in 

 this way the phenomena, so diverse, with which they 

 are associated, fermentations, putrefactions, con- 

 tagion of infectious maladies, etc. 



It is especially interesting to study the role of 

 bacteria in non-nitrogenized chemical media, where 

 they accompany the phenomena called fermenta- 

 tion, properly so called ; in nitrogenized media, 

 vegetable or animal, which they transform, as a 

 result of special fermentations, which constitute 

 putrefaction ; in the human organism, where they 

 accompany frequently, if not always, the develop- 

 ment of certain affections having special charac- 

 ters. This will be the object of so many para- 

 graphs. 



