EXERCISE XXVII. 



A STUDY OF CERTAIN COMMON SAPROPHYTIC BACTERIA. 



It is desirable to have a definite knowledge concerning 

 the characters and properties of the commonly encountered 

 species and groups of saprophytic bacteria. It is likewise 

 important to understand the method of identifying species. 

 For these reasons, a few exercises on saprophytic bacteria, 

 especially from air, milk and water, have been introduced. 



g6. Work for this Exercise. — Examine and carefully 

 describe the culture made by exposing agar and gelatin 

 plates to the air in the last exercise. Determine the 

 number of different colonies and carefully describe each. 

 Make a microscopic examination (hanging drop) of the 

 bacteria in one each of the different kind of colonies and 

 determine its genus. 



Make for examination in the next exercise a series of 

 three plate cultures in gelatin and one of two plates in agar 

 from a sample of milk furnished. The milk will be either 

 freshly drawn in sterile flasks or samples of market milk. 



Inoculate groups A and B with B subtilis from f c.al- 

 ture furnished. -v'^^- 



