12 APPLIED BACTERIOLOGY 



typhoid bacillus, the bacillus of blue milk {Bacillus cyano- 

 genus), the potato bacillus {Bacillus mesentericus vulgatus), 

 the bacillus of malignant cBdema, the hay bacillus {Bacillus 

 subtilis), Proteus vulgaris, etc. 



The following have only one or two flagella at the poles : 

 The Bacillus pyocyaneus, the Spirillum Finkleri, the Spirillum 

 cholera Asiaticm, the Spirillum Metschnikovi, etc. 



The following have numerous polar flagella : The Spirillum 

 undula, Spirillum rubrum, Spirillum concentricum, etc. 



The Micrococcus agilis has also several flagella, which 

 possibly arise from one point. 



Classification of Bacteria. — The task of classifying bacteria 

 is one of great difficulty, since they are so little known, and 

 new kinds are constantly being discovered ; also, on account 

 of the polymorphic characters of many of the forms, it is 

 only possible to arrange them in a few leading groups 

 according to their shape and general characters, such as 

 spore formation, mode of growth, etc. A great many 

 methods of classification have been put forward from time 

 to time, but the only one we will give here is a modification 

 of that proposed by Hueppe, which is the simplest and 

 most practical. The classification of micro-organisms may 

 be divided into four main divisions : 



Coccacese, Bacteriaceae, Leptotrichese, Cladotrichese. 



These groups may be again divided into groups, as 

 follows : 



Coccaceae — (1) Mic7-ococcus, or Staphylococcus. — ^When the 

 cocci occur in masses somewhat like bunches of grapes, 

 they are called Staphylococci. Cocci often occur singly, 

 sometimes in pairs, when they are known as Diplococci. 

 Some cocci are not always round, but somewhat oval ; 

 when in process of division they are necessarily more or 

 less elongated. 



(2) Streptococcus, or Chain Cocci. — Division in one 



