Medical Officers of the Army of India.

17

      This difference in the phenomena presented by portions of milk from one
and the same sample according to the level in the fluid from which they have been
obtained is a very striking one. It certainly cannot be ascribed to the presence of
any living ferments in the upper strata and absent in the lower ones, as the results
of cultivations of boiled milk showed that in all cases, and whether the fluid had
been obtained from the upper or lower strata of the sample, sterilisation had been
completely effected in regard to all organisms save Bacillus subtilis, and that
this was present throughout the entire depth. On the other hand, the occurrence
of acid fermentation and coagulation is unequivocally related to the presence and
multiplication of schizomycete organisms in the milk, so that it appears to be
probable that the explanation of the phenomenon must lie either in the actual
ferment developed by the schizomycetes and affecting the milk, having a ten-
dency to accumulate in the upper portion of the fluid, or in peculiarities in the
constitution of the latter as a material to be acted on by it. This, however, is a
point which will be again referred to in connection with an account of the results
of cultivations of specimens of boiled milk.

      Ordinary acid fermentation and coagulation thus does not occur in samples
of the lower strata of any common mass of milk as supplied in Calcutta, if these
have been once boiled so as to destroy the normal lacteal schizomycetes present
in them, and if complete sterilisation be effected, the fluid remains permanently
unaltered, save that in some cases a very slight and often fugitive acidity may
gradually manifest itself. If, however, complete sterilisation be not effected, if
the Bacillus subtilis surviving ordinary boiling remain in the fluid, whilst the
normal acid fermentation and coagulation does not occur, coagulative changes
of a different type manifest themselves at a later period. The coagulum in these
cases is not of the firm consistence of that in the case of the ordinary acid
fermentation, nor does it appear in the form of large masses but as a copious
deposit of fine powdery flocculi, easily diffused throughout the fluid, which
thus, after agitation, for a considerable time appears to casual observation as
though it retained its original characters and had not undergone any coagulative
change.

TABLE IV.—Results of Plate Cultivations of Boiled Specimens of Milk from
various sources.

D