42 PATHOGENIC BACTERIA. 



It has even been suggested to classify the bacteria by 

 the size and number of their flagella, of which so little 

 is known. 



The most convenient classification, though it cannot 

 be purely scientific, seems to be the morphological one 

 given by Cohn. Baumgarten, recognizing the relative 

 pleomorphism of certain of the species, has modified it 

 as follows, and thus made it answer all the needs of the 

 pathologist at least: 



I. Cocci, \ 



II. Bacilli, i- species relatively monomorphous. 



III. Spirilla, J 



IV. Spirulina, \ 



V. Leptothrix, I species relatively pleomorphous. 

 VI. Cladothrix,) 



The members of the first group, the cocci, bacilli, and 

 spirilla, are practically the only ones which are of patho- 

 logical significance. 



