GENERAL CHARACTERS OF BACTERIA. 



threads of bacteria, and .which may show frequent branching, a 

 characteristic not usual in bacteria. They also have a peculiar 

 method of forming reproducing bodies. The group is not one of 

 very great importance. One type of Streptothrix is extremely 

 abundant in soil and appears as round, white opaque colonies with 

 an extensive brown halo upon the plates described in Experiment 

 No. 24. 



Thus it will be seen that the term bacteria applies to the whole 

 group of organisms that multiply by division, the study of which 

 constitutes the study of bacteriology, while 

 the term Bacterium refers to a single division 

 of the group, viz. : the non-motile, rod forms. 

 The term Bacillus should apply to motile 

 forms only. The names Bacillus and Bac- 

 terium are sometimes confused; for example, 

 the tubercle bacillus, according to the above 

 classification, is a Bacterium, since it is non- 

 motile; and indeed recent study indicates that 

 it belongs to the group of higher fungi; but the 

 name bacillus was given it years before the 

 above distinctions were recognized, and we 

 will still use the common name. Some other 

 bacteria, named twenty years ago, retain their 

 earlier names in some books, but they are 



FIG. 10. Actinomy- 



slowly having their names brought into ces. a, a small colony; 

 harmony with the above distinctions. 6, .ingle rods (Bostrdm). 



The term Coccus is applied to any spherical organism of the 

 group bacteria. 



This classification gives only what are recognized as the genera 

 of bacteria. A further classification of the group into species is at 

 the present time in a condition of the greatest confusion. Many 

 hundred varieties have been described by different bacteriologists, 

 but there is great difficulty in giving any distinctive description of 

 such minute organisms, which have so few characters; and it is 

 quite uncertain whether these many hundred described species 

 represent distinct forms or whether they should be reduced to a 



