THE CHARACTERISTICS OF BACTERIA 41 



SECTION IX 

 OUTLINE FOR THE ROUTINE CULTIVATION OF BACTERIA 



In bacteriology the basis for all work is the pure culture. All 

 possible care must be taken to obtain pure cultures and to keep 

 them from contamination. The characters of most organisms 

 can only be studied to a slight extent with specimens under the 

 microscope ; the majority of their characters are determined by 

 their behavior in pure cultures on various media. The scheme 

 given below calls for cultures sufficient to determine or demon- 

 strate the characters of most organisms called for in this manual, 

 except where special directions are given. 



The student should consult the Descriptive Chart adopted by 

 the Society of American Bacteriologists (Appendix P). 



Exercise 64. Preliminary Examination 



1. Inoculate an agar-slant tube from each pure culture fur- 

 nished by the instructor or isolated from mixed infections. 

 Place the inoculated tubes in the incubator for twenty -four hours. 



2. After twenty-four hours examine the tubes for growth. 



a. Describe the growth along the stroke of the needle (see 

 Exercise 65). 



/>. Make a Gram-stained preparation. 



c. Make a simple stain with carbol-fuchsin, methylene blue, 

 or gentian violet. 



3. Inoculate the following media from the agar slant : gelatin, 

 potato, litmus milk, beef broth, and agar plate. All cultures 

 except gelatin are to be kept in the incubator. 



4. After twenty-four to forty-eight hours describe and make 

 sketches of these cultures as directed in Exercise 65. 



Exercise 65. Study of Bacterial Characters 



A. Morphology. 



1. Form and arrangement: coccus, single and grouped; 

 cliplococcwx ,' xtreptorof'f'itx ; zctrcina ; rWs, single and in 

 chains ; spiral*. 



