70 THE CULTIVATION OF BACTERIA. 



19. Square and round iron wire baskets for sterilizing test- 

 tubes (Fig. 27). 



20. Perforated tin buckets for sterilizing potatoes. 



21. Pinchcocks (Fig. 28) for holding test-tubes. 



22. Fermentation-tubes (Fig. 29). 



FIG. 31. 



Wolf huegel's ruled plate for counting colonies. 



23. A 2- and a 4-liter anatomical jar, with tightly fitting 

 cover, for the collection of blood-serum (Fig. 30). 



24. Wolf huegel's ruled plates for counting colonies (Fig. 31). 



25. Bunsen burners of different sizes. 



QUESTIONS. 



What is meant by a culture-medium ? 



What is meant by the sterilization of culture-media ? 



How is milk prepared as a culture-medium ? 



How is milk sterilized when used for a medium ? 



Why is tincture of litmus added to milk medium ? 



How does milk help in differentiating between different species of bacteria ? 



What is the process of making blood-serum ? 



How is blood-serum sterilized ? 



What is Loeffler's modification of. the blood -serum method ? 



What other animal fluids are occasionally used as culture-media? 



What does Pasteur's solution consist of? 



How would you prepare bouillon for cultures ? 



What are the principal solid cultures ? 



How would you prepare a nutrient gelatin ? 



How is nutrient gelatin sterilized ? 



What are the advantages of using gelatin as a culture ? What are its dis- 

 advantages? 



How would you prepare nutrient agar? What is difficult in the prepara- 

 tion of it? How would you sterilize it? What are its advantages and dis- 

 advantages when compared to gelatin ? 



How is agar-glycerin made ? 



What is the best way to filtrate agar? 



Give Koch's method of preparing potatoes for a culture? What are tin- 

 precautions necessary for protecting the potato from external germs ? 



