MOLDS, YEASTS, TORULAE, AND BACTERIA 187 



the second set at room temperature, and the third set 

 at25°C. ' 



4. Note which temperature is most favorable to 

 film formation. 



5. Examine under the microscope some cells from 

 the film and some from the sediment, also make per- 

 manent stained preparations. It will be observed 

 that there is a diffference in morphology between the 

 cells from the film and those from the sediment. Also 

 note the decolorization of the wort. 



6. Determine by distillation approximately the 

 amounC of alcohol produced. 



EXERCISE 4. A STUDY OF SPORE FORMATION 



1. Prepare cultures in liquid wort. 



2. Prepare gypsum blocks as described on p. 80. 



3. After growth has taken place in the tubes pour 

 oflE the supernatant fluid and smear the sediment on the 

 surface of the gypsum blocks. 



4. Incubate the gypsum blocks at 25° C. 



5. Examine a small amount from day to day until 

 spores are present, and make sketches. 



EXERCISE 5. PREPARATION OF PURE CULTURES OF 

 YEASTS FROM ONE CELL 



The preparation of pure cultures from one cell has 

 become of vast importance in breweries. It is rela- 

 tively diflScult to prepare pure cultures of bacteria 

 from one cell, these being smaller than yeasts and, 

 therefore, more diflScult to manipulate. Barber 

 {Jour. Infect. Dis., 1908, 5, p. 379) has succeeded in 

 devising a practical method for isolating single cells of 

 bacteria and preparing pure cultures from these. 



