MICROBES. 185 



MICROBES. 



By the name microbes are understood beings of ex- 

 ceeding smallness, that can be seen only by the aid of 

 powerful microscopes ; they are less than one-ten-thou- 

 sandth of an inch in diameter, but their number is so 

 large that it compensates for their minute size. 



These beings take a very important part in nature. 

 In particular, they appear to be the causes of all the 

 putrefactions and fermentations with which we are 

 acquainted. Besides, many of them live as parasites in 

 the blood or in the organs of men and other animals, 

 and by their presence occasion the most serious diseases. 

 It is now proved that all the contagious affections are 

 caused by microbes : thus, the anthrax, or carbuncle, 

 which sometimes decimates cattle, hydrophobia, typhoid 

 fever, intermittent fever, scarlet fever, measles, cholera, 

 etc., are due to the presence of specific microbes in the 

 blood or in some part of the organism. It is impossible 

 for us to enter into minute details concerning these 

 little creatures, and we can only indicate their more 

 common forms. In this respect they may be divided 

 into two classes : the ones called monads are globular ; 

 the others are filiform. The latter are sometimes 

 straight, as the bacterium of carbuncle, sometimes un- 

 dulating, as the vibrios, sometimes curled in a spiral, as 

 the spirillum, 



The bacteria of malignant anthrax, which we will 

 take as an example, consist of rigid, straight, cylindri- 

 cal filaments, at the most about one twenty-five-hun- 

 dredth part of an inch in length. These filaments are 

 immobile, which distinguishes them from ordinary bac- 

 teria and vibrios and spirilli. The bacteria of anthrax 



16* 



