190 Medical Bacteriology. 
Esner’s Medium. Method of preparation: 
Peel and cut up 500 gms. of old potatoes of medium size, add 1000 ce. of water and 
boil 1 and 4 hours. 
Mash potatoes thoroughly; strain through a cloth and add water to filtrate to make 
a liter. 
Add 15 % gelatin and boil 10 minutes. Cool to 60° C. and add white of one egg 
and boil 15 minutes. 
Filter through cotton, then paper. Titrate and make gelatin 2-3 % acid. Just before 
tubing add 1 % potassium iodide (10 ce. of a solution in which 1 ce. contains 1 gram of 
potassium iodide). Tube and sterilize three times. 
Plates of this medium are made in the usual way and kept at 15-18°C. On this me- 
dium the typhoid germ forms very finely granular, small, bright droplets resembling 
condensed moisture, while the colon bacillus gives rise to larger, brown colonies, which 
are more granular and spread more. 
Hiss’ Plate Medium. This contains: 
10 grams of agar. 
25 grams of gelatin. 
5 grams of beef extract (Leibig). 
5 grams of sodium chloride. 
10 grams of glucose. 
1000 grams of water. 
_ It is made by first dissolving the agar, salt and extract in the water, then the gelatin 
is added and dissolved, the reaction changed by use of NaOH and phenolphthalein so 
that it will contain not less than 2% normal acid, cleared with two eggs and filtered, glu- 
cose added and the medium tubed and sterilized. 
Make plate cultures in ordinary way and incubate at 38° C. for 18 hours, then ex- 
amine the colonies microscopically. The colonies of B. typhosus have irregular out- 
growths and fringing threads. The colonies of B. coli, on the other hand, are much large 
and as a rule are darker in color and do not form ehyaada, 
The colonies may be further examined by the use of Hiss’ Tube Medium. 
5 grams of agar-agar. 
80 grams of gelatin. 
5 grams beef extract (Leibig). 
5 grams sodium chloride. 
10 grams glucose. 
1000 grams water. 
Made as plate medium except that is is to contain 1.5% normal acid. 
Within 18 hours at 38° C. the typhoid bacilli produce a uniform clouding. The 
colon bacilli do not produce uniform clouding and do produce gas. 
All suspected cultures should be tested with typhoid blood (Widal reaction). 
The typhoid organism may be isolated from the stools during the first two weeks of” 
the disease. 
MICROSPIRA COMMA. 
1. Microscopical examination of ‘‘rice-water’’ discharges for spirilla lying parallel. 
2. Culture methods. Gelatin or agar-plates should be made from the rice-like flakes; 
other flakes should be inoculated into flasks of peptone water (Dunham’s solution) and 
inoculated at 38° C. The surface growth 6-12 hours later is to be examined microscop- 
