THE CLASSIFICATION OF BACTERIA 53 



EXERCISE XIV 



THE CLASSIFICATION OF BACTERIA 



81. The term " bacteria " is a general and popular one used 

 to designate a large group of microscopic plants, the Schizo- 

 mycetes. These organisms, which are widely distributed in 

 nature, have been classified into a certain few famihes and 

 genera most of which have a large number of species. Many 

 of these species have been described, but there are many which 

 have not. In classifying the bacteria, the genera are based on 

 morphologic characters ; while, as a rule, the species are deter- 

 mined by means of their biochemic, physiologic, or pathogenic 

 properties. Several systems of classification have been pro- 

 posed, but the one which seems to be the most satisfactory is 

 by Migula. This classification utilizes the morphology to such 

 good advantage that its adoption seems desirable. It requires, 

 however, some serious changes in the accustomed nomen- 

 clature; but this is true of any logical system. The restoration 

 of the genus Bacterium and the assigning to it of all non- 

 motile, rod-shaped organisms change the genus of some of 

 our most common pathogenic bacteria from Bacillus to Bac- 

 terium. The most conspicuous of these are the bacilli of 

 tuberculosis, glanders, and diphtheria, all of which are placed 

 in Migula's classification in the genus Bacterium. The families 

 and genera recognized by him are appended. (See lecture notes 

 and text-books on the classification and morphology of bacteria.) 



82. "Work for this exercise. Read the references on the 

 morphology and classification of bacteria. 



Reject all the cultures made and clean the tubes and Petri 

 dishes [§ 3, (/)]. 



Inoculate a tube of bouillon (from cultures which will be 

 furnished) with each of the following genera of bacteria : (i) a 

 streptococcus, (2) a micrococcus, (3) a sarcina. 



