FECAL AND NON-FECAL B. COLI 309 
adonite broth and gelatin. For additional confirmatory evidence 
inoculation may be made into tryptophane broth and saccharose broth. 
The dextrose broth must be incubated at 30°. Other sugar broths may 
be incubated at 30° or 37° as convenient. Gelatin should be incubated 
at 20°. 
(3) After forty-eight hours record gas formation in adonite and 
saccharose broths. Determine indol formation in tryptophane broth 
by adding, drop by drop, to avoid mixing with the medium, about 1 e.c. 
of a 2 per cent alcoholic solution of p-dimethyl amido-benzaldehyde, 
then a few drops of concentrated hydrochloric acid. The presence of 
indol is indicated by a violet color. 
(4) After five days apply methyl red test and Voges-Proskauer test 
to dextrose broth. 
Mertruyit Rep Trstr 
Indicator Solution. Dissolve 0.1 gm. methyl red in 300 e¢.c. alcohol 
and dilute to 500 c.c. with distilled water. 
Procedure in Test. 1. To 5 c.c. of each culture add five drops of 
methyl red solution. 
2. Record distinct red color as methyl red+, distinct yellow color 
as methyl red—, and intermediate colors as ?. 
VoGEs-PROSKAUER TEST 
To the remaining 5 ¢.c. of medium add 5 c.c. of a 10 per cent solution 
of potassium hydroxide. Allow to stand over night. A positive test 
is indicated by an eosin pink color. 
(5) Gelatin tubes should not be pronounced negative until they 
have been incubated at least fifteen days. 
The following group reactions indicate the source of the culture 
with a high degree of probability. 
Methyl red+ 
Voges-Proskauer — 
Gelatin — 
Adonite— 
Indol, usually — 
Saccharose, usually — 
B. colt of fecal origin 
