CHAPTER III. 



MICROBES, STRICTLY SO CALLED, OR BACTERIA. 



I. THE VEGETABLE NATURE OF MICROBES. 



As we have seen in the preceding chapter, there is 

 no well-defined limit between ferments and bacteria, 

 any more than between ferments and fungi, or, again, 

 between fungi and bacteria. Their smaller size is the 

 principal difference which separates bacteria from 

 ferments, since in other respects these two classes are 

 for the most part alike in form and organization. There 

 are bacteria of large size, such as Leptothrix buccalis, 

 so frequently found in the mouth even of a healthy 

 man, which much resembles in its mode of growth 

 some of the lower fungi, such as Oidium albicans. 

 Yet the latter is regarded as a fungus, and the former 

 as an alga, by our best cryptogamous botanists. It 

 may, however, be said that the two classes of algae and 

 fungi are connected with each other by their lower 

 forms, and probably have a common origin ; just as the 

 two great organic kingdoms are connected by their 



