16
Scientific Memoirs by
This fact was first ascertained accidentally during the course of a series of
operations devoted to the attempt to obtain a sufficient stock of sterilised milk
to form the basis for experiments on the phenomena following inoculations of
Comma-Bacilli. For some time these proved unsuccessful, due to the fact that
the milk, even if boiled more than once in carefully sterilised vessels, either had
coagulated spontaneously within the course of 24 hours or underwent full coagula-
tion and separation on being boiled anew after that interval. In the course
of these attempts it was observed that residual portions of milk treated with less
care than the rest of the fluid, and representing the residue of the stock supply
remaining in the vessel in which it had been obtained, sometimes remained un-
altered when those which had been treated with special care had undergone
change. Attention having thus been attracted to differences in the strata of the
milk as determining the different phenomena presenting themselves under what
otherwise appeared to be uniform conditions, a series of experiments was directed
to the investigation of the point, and by siphoning off specimens from the upper
and lower strata of identical samples of milk it was clearly shown that, whilst a
single boiling sufficed to secure an abolition of the normal acid fermentation
and coagulation of specimens from the lower strata, a similar treatment failed to
do so with specimens taken from the top.
When the phenomenon of normal coagulation and acid fermentation occur-
ring in spite of the specimens having been boiled first presented itself, it
appeared not impossible that it was related to atmospheric conditions and
especially to elevation in temperature, as it did not manifest itself in any of
the first samples of the series obtained in the beginning of the year and when
the temperature was relatively low. The earliest example in which the pheno-
menon manifested itself was in a sample of milk obtained on the 8th of
March, whilst in May, at a time when the temperature was very high, it occurred
as a normal event. On the recognition of the different relations which different
strata of one and the same specimen of milk bear to the occurrence of the
phenomena, it appeared, however, probable that the different results obtained
in connection with the different periods of year were really related to these, and
not to conditions of temperature. The earlier samples were portions of milk in-
troduced directly into sterilised tubes from that presented for use at table, and
may very well in some cases have been derived from the lower stratum of the
entire bulk of the fluid representing the house-supply; in only one of them—that
obtained on the 8th March—did coagulation and acid fermentation occur subse-
quent to boiling. The samples from the 15th March onwards were obtained in
large quantity and direct from the bazaar, from the milkman who furnished the
house, or in two instances from the Zoological Garden, and until attention had been
attracted to the influence of strata, the individual specimens kept under observa-
tion were obtained by pouring off milk from the stock-supply and, therefore, must
have corresponded with superficial strata of it.