SYSTEMATIC STUDY OF SPECIES OF BACTERIA. 113 



Growth on culture-media. 

 9. Relation of growth to temperature. 

 10. Gelatin; observe whether the gelatin is liquefied or not. 

 Colonies in gelatin plains, study under low power of 

 microscope. 



n. Agar. Colonies in agar plates, study under low power 

 of microscope. 



12. Bouillon; note cloudiness, pellicle or precipitate. 



13. Milk; observe the reaction and whether or not the milk is 



coagulated 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 luxuriant 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 important 

 culture-media. Having culture-media prepared, it is custom- 

 ary to study a number of species of non-pathogenic bacteria. 

 Notes of the work and sketches showing the morphology of the 

 organisms should be made. In this as in other work with the 

 microscope, the value of even crude drawings is very great as a 

 matter of training. It is well to choose species which have 

 properties decidedly different from one another. The micro- 

 cocci, 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 



