DISTINCTIVE CHARACTERS OF THE BACTERIA. 177 



to a small group of similar species of bacteria is fixed. 

 The distinction of these closely similar species is then 

 easily made by the aid of some very characteristic 

 reagent, or is a complicated study, and can only be 

 done by observing the appearance of the growths in 

 stroke or puncture cultivations, by studying the action 

 of the cultivation on animals, &c. 



Formerly Cohn made the attempt to distinguish a large Cohn's former 

 number of species of bacteria on the basis of their morpho- c a j| sincatior 

 logical characters. But exactly similar morphological pecu- schizophytes. 

 liarities occur in the lower algae ; and it |is essentially only 

 the absence of chlorophyll which separates the fungi from the 

 vilgae ; on this point however, as has been said above, no 

 special weight is now laid. And thus when special attention 

 is paid to the morphological characters, the resulting classi- 

 fication of the " schizophytes," must include fission fungi 

 and fission alga3. Such a classification is certainly admirably 

 adapted for placing in correct light certain similarities and 

 differences between the lower algae and fungi, but it is not 

 sufficient for the number of species now discovered, and it no 

 longer meets practical wants, more especially because a 

 number of heterogeneous organisms of unequal value from 

 <i hygienic standpoint are mixed together. In the former 

 edition of this handbook the author attempted by omitting 

 the algae to transform Cohn's classification in the following 

 manner so as to be useful for a circle of readers composed 

 chiefly of medical men : 



12 



