70 MEDIA AND THEIR PREPARATION 
Serum Agar. 1. Dissolve 1.5 grams of agar in 100 c.c. distilled 
water. Filter, tube (5 ¢.c. in each tube) and sterilize. 
2. Coolto 40°C. To each tube add an equal volume of sterile serum. 
Mix gently by rolling the tube and cool in a slanting position. 
Alkaline Blood Agar (Dieudonne). Mix equal volumes of bovine 
blood and a normal solution of potassium hydroxide. Steam for one- 
half hour; mix three volumes of this alkalin blood with seven volumes 
of neutral (to litmus) meat broth agar and pour plates. Dry the plates 
at 60° C. for half a hour and keep at room temperature for at least 
twenty-four hours before using in order to free them from ammonia, 
the evolution of which would prevent the growth of Mzcrospira cholerae. 
(Quoted from Goldberger, 1913.) 
Alkalin Hemoglobin Agar for Microspira Cholerae (Esch, 1910). 
Dissolve 5 gms. of horse hemoglobin (Merck) in 30 ¢.c. of a half normal 
sodium hydroxide solution. Steam for one-half hour. Mix 15 c.c. 
of this alkalin hemoglobin solution with 85 c.c. of neutral (to litmus) 
meat broth agar, pour plates and dry at room temperature with covers 
removed. The plates are ready for use as soon as dry—a matter of 
about a half a hour. (Quoted from Goldberger.) 
Mix Mepia 
Casein Agar (Ayres, 1913). Preparation of 1 liter. 
Casein solution: 
300 c.c. distilled water. 
10 gms. casein (Eimer & Amend C.P. casein prepared accord- 
ing to Hammarsten). 
7 ¢c.c. normal sodium hydroxide. 
Agar solution: 
500 c.c. distilled water. 
10 gms. agar. 
After dissolving casein make up to 500 cubic centimeters. 
To 300 c.c. of water (distilled) add: 
10 gms. casein (Eimer & Amend C.P. casein prepared accord- 
ing to Hammarsten). 
7 ¢.c. normal sodium hydroxide. 
Dissolve casein by heating to boiling. It is desirable to let this 
solution stand for several hours to get a perfect solution. This is 
not necessary, however. Make up volume to 500 ¢c.c. and bring the 
