r hand, but
in the case of our special soured milk we kill out, practically, all
wild bacteria and germs, and the pure culture having the field to
itself, we can conduct the operation at a higher temperature where the
action of the bacteria is at its maximum, and so obtain the necessary
lactification in the minimum of time.

The appliances for the souring of milk on the domestic scale require
some consideration. We propose to describe the principal forms of
apparatus which have been put on the market for the purpose, and then to
give such suggestions as may assist the ingenious in making apparatus
for themselves. Those who wish for information on the subject of larger
apparatus will find it in the following chapter.

[Illustration: FIG. 41--Photograph of Agar Culture,
inoculated with a lactic powder offered to consumers under
a fancy name. Working on the assumption that the presence
of lactic bacteria is inimical to the growth of septic
organisms, this preparation has been placed on the market.

The plate shows, however an abundance of colonies of
foreign organisms--sporogenous bacilli, _Staphylococcus
pyogenes albus_, and _Staphylococcus pyogenes aureus_.
These organisms are shown in the appended
photo-micrographs, and constitute impurities in the
preparation.]

[Illustration: Spore forming bacillus]

[Illustration: _Staphylococcus pyogenes albus_]

[Illustration: FIG. 42--Photograph of Test Tubes of Sterile
Milk, inoculated with a tablet preparation said to contain
pure cultures. The darker liquefied portion of the
tube-contents is due to digestion of the curd by
proteolytic bacteria, thus indicating impure culture. Pure
cultures of lactic acid bacteria coagulate the milk
uniformly, but do not produce any subsequent change in the
appearance of the culture, even after several months.]

[Illustration: FIG. 43--Photograph of Test Tubes of
Sterile Milk, each tube having been inoculated with a
tablet of a preparation said to contain pure cultures.
Here, again, there is evident peptonisation of the curd,
thus indicating infection by proteolytic ferments.
Cultures from these tubes demonstrated the presence of a
foreign organism. Microscopical examination failed to
disclose the presence of _Bacillus Bulgaricus_.]

[Illustration: FIG. 44--Photograph of Test Tubes of
Sterile Milk, inoculated with a tablet of
"Lactobacilline." In contra-distinction to