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. n). 



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 keep 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 liters of water 

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



