VOGES-PROSKAUER REACTION 307 
and hydrogen while those from grains formed two or three times as 
much carbon dioxide. The next step was to find a simple procedure 
for determining this ratio or finding some procedure which was correlated 
with it since the determination of the gas ratio is too exacting for routine 
analyses. Clark and Lubs (1915) working in the same laboratory dis- 
covered a constant correlation between the gas ratio and the hydrogen 
ion concentration. The B. cols from bovine feces were found to possess 
a higher hydrogen ion concentration than those from grains or non- 
fecal origins. A study of indicators yielded the information that methyl 
red was yellow with the high ratio group and red or acid with the low 
ratio group. Levine (1916) correlated this test with the Voges-Pros- 
kauer reaction. 
Voges-Proskauer Reaction. This has been studied by Levine who 
correlated it with the methyl red test. He found the bacteria which 
give the Voges-Proskauer reaction were rarely found in feces and that 
the Voges-Proskauer reaction, like the high gas ratio and the alkalinity 
to methyl red, is characteristic of non-fecal strains and, therefore, of 
much sanitary significance. Harden (1901), in his various publications, 
has reported his studies on the chemistry of this reaction which are well 
reviewed by Levine. The red color which results is due to a definite 
end product in the fermentation of glucose. Voges and Proskauer 
(1898), in their original publication, describe the test as follows: 
“On addition of caustic potash, we observed a new and interesting 
color reaction. If the tube be allowed to stand twenty-four hours and 
longer at room temperature, after the addition of the potash, a beautiful 
fluorescent color somewhat similar to that of a dilute alcoholic solution 
of eosin forms in the culture fluid particularly at the open end of the 
tube exposed to the air. We have investigated a few of the properties 
of this coloring substance which is not produced by the action of the 
alkali on the sugar and have found that it is fairly resistant to the action 
of the external air. .After a time, however, it becomes paler, and 
finally gives place to a dirty greenish brown.” 
Harden and Walpole (1905-6) could not account for all of the car- 
bon in the dextrose by the ordinary products (organic acids, alcohol, 
etc.) along with these substances was secured a glycol which was made 
up of 2: 3 butylene glycol. 
LETT 
ase 
H OH OH H 
