In glucose-bouillon, butyric and lactic acids are formed and the
reaction of the medium becomes distinctly acid. Butyric and lactic
acids were also noted in the egg-pork cultures.
A series of Smith fermentation tubes containing 10 c. c. each of
glucose-pork broth medium was inoculated with the bacillus and held
at room temperature (20° to 25° C.). These cultures were titrated
against [N/40]NaOH, with phenolphthalein as an indicator at intervals
of two days up to nineteen days, and then at two-week intervals up to
sixty-one days. Three of the cultures were titrated each time so as to
give a fair average of the acidity of the cultures, and an uninoculated
check tube was also titrated each time to see if there was any change
in the reaction of the medium. The results of the titrations are shown
in the following table:
_Acidity determinations in glucose-pork broth cultures._
──────────────┬───────┬───────┬───────┬────────┬───────┬───────────
Age of culture│Culture│Culture│Culture│Average.│Medium.│Acidity of
(days). │ A. │ B. │ C. │ │ │ culture.
──────────────┼───────┼───────┼───────┼────────┼───────┼───────────
│ │ │ │ │ │_Per cent._
2 │ 0.038 │ 0.030 │ 0.040 │ 0.036 │ 0.009 │ 0.027
4 │ .105 │ .100 │ .102 │ .102 │ .009 │ .093
6 │ .106 │ .110 │ .109 │ .108 │ .009 │ .099
8 │ .124 │ .115 │ .117 │ .119 │ .009 │ .110
10 │ .128 │ .130 │ .126 │ .128 │ .009 │ .119
12 │ .129 │ .120 │ .129 │ .126 │ .009 │ .117
19 │ .126 │ .125 │ .125 │ .125 │ .009 │ .116
33 │ .125 │ .123 │ .125 │ .124 │ .009 │ .115
47 │ .122 │ .120 │ .121 │ .121 │ .009 │ .112
61 │ .121 │ .116 │ .119 │ .118 │ .009 │ .109
──────────────┴───────┴───────┴───────┴────────┴───────┴───────────
From the above table it will be seen that the maximum acidity was
reached at ten days, after which there was a gradual reduction in the
acidity, due probably to the formation of ammonia compounds.