CLASSIFICATION OF THE BACTERIA. 51 



Fat globules, which are found of all sizes, are 

 often of the same dimensions as Micrococcus, and 

 are very difficult to distinguish from the latter. 

 The difference in refractive power is slight, and 

 the action of re-agents, such as ether, is not cer- 

 tain in mucilaginous solutions. Hiller, who has 

 paid especial attention to the means of recognizing 

 bacteria, divides them into two groups : — 



A. The optical signs : comprising 1. The charac- 

 teristic vegetable form, rods, leptothrix, this he 

 recognizes as of little use, as in this case there is 

 no doubt; 2. The characteristic movements of the 

 monads; 3. The mode of growth and of multipli- 

 cation ; 4. The mode of junction of the granules. 



B. The chemical signs : 1. False zoogloea become 

 softened and diffluent under the action of liq. 

 potassae, and are coagulated by the direct applica- 

 tion of alcohol ; 2. In sections of tissues, after an 

 hour of maceration in liq. potassae, diluted y^th, 

 the monads are colored brown by iodine, while fat 

 granules are not. 



But, in truth, the method of cultivation, ex- 

 tolled by Cohn and Wollf, is the best means of 

 distinguishing the bacteria. " The distinction of 

 pseudobacteria," says the first of these authors, 

 " from veritable globular bacteria is a problem 

 which our microscopists cannot resolve, in every 

 case, with the desirable certainty. It is only by 

 a study of their mode of development that this 

 distinction can be made. The globules which di- 

 vide and develop in form of chains are organized 

 beings ; when this does not occur, we are dealing 

 with pseudobacteria." 



