126 BIOLOGY AND TECHNIQUE 



Calcium Carbonate Broth. — This medium is designed for obtaining 

 mass cultures of pneumococcus or streptococcus for purposes of im- 

 munization or agglutination. 



To 100 c.c. of meat infusion broth in small flasks, add one per cent 

 of powdered calcium carbonate, and one per cent of glucose. It is a 

 wise precaution to sterilize the dried calcium carbonate in the hot-air 

 chamber before using. Small pieces of marble may be used as sug- 

 gested by Bolduan. 



Pepton-Salt Solution (Dunham's solution): 



1. Distilled water 1,000 c.c. 



Pepton (Witte) 10 gms. 



NaCl 5 " 



2. Heat until ingredients are thoroughly dissolved. 



3. Filter through filter paper until perfectly clear. 



4. Tube twenty-five tubes, and store remainder in 250 c.c. flasks. 

 Sterilize by discontinuous method. 



Nitrate Solution. — 



1. Distilled water 1,000 c.c. 



Pepton 10 gms. 



Potassium nitrate 0.2 " 



2. Heat until ingredients are thoroughly dissolved. 



3. Filter through filter paper until perfectly clear. 



4. Tube twenty-five tubes, and store remainder in 250 c.c. flasks. 

 Sterilize by discontinuous sterilization. 



Uschinsky' sProteid-Free Medium.^ — To one liter of distilled water add : 



Asparagin 3.4 grams. 



Ammonium lactate 10 



Sodium chloride 6 



Magnesium sulphate 0.2 



Calcium chloride 0.1 



Potassium phosphate 1.0 



When these substances are thoroughly dissolved, add 40 c.c. of glycerin 

 Tube and sterilize. 



Gelatin. — Meat-Extract Gelatin. — 1. To 1,000 c.c. of distilled water 

 add Liebig's extract 5 gms., pepton 10 gms., NaCl 5 gms., and 120 

 gms. of the finest French sheet gelatin.^ 



' Uschinsky, Cent. f. Bakt., 1, xiv, 1893. 



2 The acidity and consistence of the different commercial gelatins vary con- 

 siderably and care should be taken in selecting a uniform and suitable brand, such as 

 Hesterberg's gold label gelatin. It is advisable, when working during the summer 

 or in hot climates, to add 130 instead of 120 grams. 



