REMOVING MICROORGANISMS FROM LIQUIDS 145 



7. Make pure cultures on agar slants from three differ- 

 ent well-isolated colonies of the predominant types and in- 

 cubate at room temperature. 



8. Examine these in thirty-six to forty-eight hours 

 in a hanging drop for morphology and spore formation. 



9. Make a spore stain as soon as spores are found. 

 Where are the spores located in the bacterial cell? 



10. Have you studied any pure culture of bacteria which 

 is similar to the types you have isolated? What organism 

 is commonly found in hay? In what form does it exist on 

 the hay? What do you know of the habitat of this organ- 

 ism and related forms? Of the pathogenicity? 



11. State the results obtained in detail; draw the con- 

 clusions which follow and point out any possible practical 

 applications. 



REFERENCES 



MARSHALL: Microbiology, pp. 5, 45, 154, 189, 242. 

 JORDAN: General Bacteriology, 4th Ed., pp. 235-236. 

 EYRE: Bacteriological Technic, 2d Ed., p. 140. 



EXERCISE 50. TO DEMONSTRATE THE EFFICIENCY 

 OF FILTRATION AS A MEANS OF REMOVING 

 MICROORGANISMS FROM LIQUIDS 



Apparatus. Six small funnels; two small filter papers; 

 two small pieces of absorbent cotton; two small pieces of 

 clean hospital gauze; eight tubes sterile agar; eight sterile 

 Petri dishes; ten sterile 1 c.c. pipettes; sterile 10 c.c. 

 pipette; three dilution flasks; six sterile test tubes; tube 

 of sterile broth. 



Culture. B. coli. 



Method. 1. Inoculate broth with B. coli and incubate 

 for twenty-four hours at 21 C. 



2. Sterilize filter paper in each of the two small funnels, 

 a small piece of absorbent cotton in each of two more; 

 fold two pieces of clean gauze several thicknesses and 



