Medical Officers of the Army of India.
33
this procedure the capacity for co-existence of Comma-Bacilli with Bacillus sub-
tilis in a medium already thickly populated by the latter organism was most
satisfactorily determined. Apart from the length of interval between the opera
-tions of boiling and inoculation, the conduct of all the experiments was practi
-cally identical. The samples of milk, having been briefly boiled in sterilised test
tubes over an open flame, were kept in the incubator until the period when inocu
-lation was performed. During the interval they underwent the changes charac
-teristic of specimens of milk occupied by pure growths of Bacillus subtilis in
greater or less degree—pulverulent coagulation, frequently a tendency to slight
development of acid, and in some cases the evolution of a foul putrescent
odour. Inoculation was conducted in the same fashion as it was in the case of
the experiments on unboiled samples of milk.
The results of cultivations subsequent to inoculation varied in character
considerably, apparently in relation to the period which had elapsed between the
introduction of the Comma-Bacilli into the milk and the establishment of the
cultivation. Those cultivations which were set at a period of 24 hours subsequent
to inoculation always yielded excessively abundant crops of colonies of charac
-teristic Comma-Bacilli. At the same time there were evidences of apparent par
-tial suppression in the development of Bacillus subtilis in the milk, as, though
the cultivations were in no instance pure cultivations of Comma-Bacilli, the
amount of the other species which was present was very small, the growth being
confined to more or less extensive, but very thin, diffused strata spread over the
surface of the gelatine. The development of Bacillus subtilis in cultivations set
at this period resembled that manifesting itself in connection with some cultiva
-tions of unboiled and non-inoculated milk, and not that normally present in speci
-mens of milk containing Bacillus subtilis alone as their living schizomycete con
-tent. The cultivations had a strong characteristic choleraic odour, and the films
of Bacillus subtilis were so thin as in many cases to render their direct recogni
-tion almost impossible, even where their presence had been ascertained due to the
contamination of preparations of the colonies of commas by distinct rods of the
other species.
The presence of very large numbers of Bacillus subtilis in specimens of boiled
milk does not, therefore, serve to prevent the occurrence of very rapid growth
and multiplication of Comma-Bacilli which may gain access to the medium.
There is no rapid suppression of the multiplication and vitality of the Comma-
Bacilli such as is normally present in cases where the medium has not been boiled,
and the intrusion of the Comma-Bacilli appears, on the contrary, to give rise to
partial and temporary suppression in the development of the pre-existent schi
-zomycete population represented by Bacillus subtilis.
This suppression and the excessive multiplication of Comma-Bacilli seems,
however, to be of comparatively brief duration, for cultivations set after longer
intervals from the period of inoculation frequently show a great reduction in