GELATIN MEDIA 50 
a close separation between B. coli and B. aerogenes. Levine describes 
its preparation as follows: 
Distilled water... 0.0.0.0... 0.0 c cee cee eee 1000 c.c. 
Peptone (Difco)..........0 0.0.0. 0c ee ee eee 10 gms. 
Dipotassium phosphate.................... 2 gms. 
AQOr. 20 icc cece eee eee eee 15 gms. 
Boil the ingredients until dissolved and make up any loss to evapo- 
ration. Place measured quantities in flasks and sterilize at 15 lbs. for 
fifteen minutes. Just prior to use add to each 100 c.c. of the melted 
agar prepared as above, the following constituents: 
Sterile (20 per cent lactose). ............0008- 1 gm. or 5 e.c. 
Aqueous (2 per cent) eosin (yellowish) solution. 2 @.c. 
Aqueous (2 per cent) methylene blue solution. 2 C.¢. 
Pour the medium into dishes allow them to harden in the incubator 
and inoculate in the usual way. There should be no adjustment of the 
reaction and filtration of the medium is not necessary. 
GELATIN MrEpIA 
Nutrient Gelatin. 1. Add 3 gms. of beef extract and 5 gms. of pep- 
tone to 1000 c.c. of distilled water and add 100 ems. of gelatin dried for 
one-half hour at 105° C. before weighing. 
2. Heat slowly on a steam bath to 60° C. until the gelatin is dissolved. 
3. Make up lost weight, titrate, and if the reaction is not already . 
between +0.5 and +1, adjust to +1. 
4, Filter through cloth and cotton until clear. 
5. Distribute in test tubes, 10 ¢.c. to each tube, or in larger contain- 
ers if desired. 
6. Sterilize in the autoclave at 15 lbs. (120° C.) for fifteen minutes 
aiter the pressure reaches 15 lbs. 
Whey Gelatin. Add 10 per cent to clarified whey. This medium 
is of value in studying’ certain members of the lactic acid bacteria. 
Soil Extract Gelatin (Conn, 1914). 
Gelatin 2.0.0... c ccc ee ee eee eee 100-150 gms 
Dextrose... 0.0... cc cee ete ees 1 gm 
Soil extract... 6... cece eee eee ee eee eee 100 c.c 
