CHAPTER VIII. 



SYSTEMATIC STUDY OF SPECIES OF BACTERIA.* 



In order to conduct the study of any species of bacteria it is 

 necessary to have the organism isolated in a pure culture. 

 This is best accomplished by the plate method already de- 

 scribed. Having thus obtained the organism in pure culture, 

 it is to be examined with reference to its behavior in certain 

 particulars. It is well for the beginner to study a few known 

 species of saprophytes obtained from some reliable laboratory 

 in pure culture. The points which are to be considered can 

 be illustrated best by presenting them in tabular form, filling 

 out the items of the table for a given species of bacteria. 



1. Name. 



2. Habitat or source. 



3. Morphology; grouping, as in chains or in zoogloea;. 



4. Size. 



5. Staining properties. Behavior by Gram's method. 



6. Capsule, present or otherwise. 



7. Spore formation. 



8. Motility, flagella. 



Observations as to morphology, grouping, size, staining prop- 

 erties, and motility should all be made on fresh cultures. Agar 

 cultures from 18 to 24 hours old are usually selected for the 

 purpose. This rule cannot always be adhered to from the 

 nature of the case as, for example, in the examination of cultures 

 of the tubercle bacillus, of the gonococcus, of the diphteria bacil- 

 lus. Examination for the presence of spores may also require 

 older cultures. 



*See Appendix I., for recommendations of Society of American Bacteriologists. 



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