SYSTEMATIC STUDY OF SPECIES OF BACTERIA. 113 



11. Agar. Colonies in agar plates, study under low 



power of microscope. 



12. Bouillon, note cloudiness, pellicle, or precipitate. 



13. Milk; observe whether or not the milk is coagu- 



lated and subsequently peptonized. 



14. Production of gas in fermentation-tube with bouillon 



containing sugar, as dextrose, or in agar with 

 sugars. 



15. Potato. 



1 6. Blood-serum; observe whether or not peptonization 



occurs. 



17. Production of indol. 



1 8. Pigment formation. 



19. Production of acid or alkali. 



20. Relation to oxygen; observe whether the superficial 



or the deep part of the growth is the more luxu- 

 riant in stab-cultures; use anaerobic methods if 

 necessary. 



21. Pathogenesis. 



In commencing the study of bacteriology the pupil should 

 try the common staining methods and make the most im- 

 portant culture-media. Having culture-media prepared, it 

 is customary to study a number of species of non-pathogenic 

 bacteria. Notes of the work and sketches showing the mor- 

 phology of the organisms should be made. It is well to 

 choose species which have properties decidedly different 

 from one another. The micrococci, bacilli and spirilla 

 should be represented; forms that are motile and that are 

 not; species that form spores and others that do not form 

 spores; some that liquefy gelatin and some that do not. 

 There should be chromogenic forms, and species that fer- 

 ment dextrose, and that produce indol, such species as 

 some of the sarcinse, the bacillus coli communis, the hay 

 bacillus, the potato bacillus, bacillus prodigiosus, a bacillus 



