32 LABORATORY GUIDE IN BACTERIOLOGY 



2. Three parts of serum are mixed with i part 

 broth containing i . 5 per cent dextrose. 



3. The mixture is filtered and tubed. 



4. Place in a Koch inspissator (Fig. 11). 



5. Incline the inspissator to the proper angle, so as 

 to produce a large sloping surface of the serum. 



6. Heat slowly to the boiling point and boil for 5 

 minutes. This process is to be repeated on three or 

 four successive days. 



Note. — 25 c.c. water should be placed in the inspissator with 

 the tubes, so as to licep the air in the inspissator saturated. 

 Blood serum may be sterilized in a shorter time by the use of 

 the autoclave (see p. 16). 



EXERCISE 10. PREPARATION OF BEERWORT MEDIA 



Hopped beerwort may be obtained from a brewery. 

 Beerwort media are used chiefly for the cultivation of 

 yeasts and molds, these preferring media of the acidity 

 of beerwort. Beerwort should be autoclaved, cooled, 

 and filtered before tubing, otherwise a precipitate will 

 form in the tubes. 



Liquid beerwort. — Place about 7 c.c. of beerwort in 

 culture tubes and sterilize at 120° C. for five minutes. 



Beerwort gelatin. — Dissolve 10 to 12 per cent gold 

 label gelatin in beerwort and sterilize at 120° C. in the 

 autoclave. 



Beerwort agar. — Dissolve i . 5 per cent agar in beer- 

 wort and sterilize at 120° C. in the autoclave. 



EXERCISE II. PREPARATION OF YEAST-WATER MEDIA 



Yeast water, — One liter of washed yeast or one 

 pound of pressed yeast is boiled in two hters of water 

 for one hour. The reaction is made neutral to phenol- 



