cotton,
granulated cork, or washed cow hair packed between two-inch by six-inch
battens, covered with matching on either side, and lined with sheet
zinc. It would be an advantage to have an air-lock or anteroom into
which the waggons or trays of sterilised jars could be run, and the door
of the anteroom closed before the door of the insulated room is opened.
This would tend to prevent variations of temperature in the room, and
also, by checking free communication with the outside air, decrease
contamination. The waggons of jars would be run in, and culture added to
each jar by a sterilised pipette. The atmosphere of the room would be
kept pure by running in air frequently through a filter of moist
cotton-wool by means of an electric fan, and at intervals the interior
would be sterilised by the use of formalin vapour.

[Illustration: _Details of an American Apparatus for
Preparing Soured Milk_

FIG. 57

The figures give diagrams A, B, C, and D of an apparatus
useful for the preparation of lactic foods. The incubating
can A, is made of block tin, and is intended to contain
the milk. B, the warm water container, should be a stout
walled vessel with a circular aperture in the lid, through
which the incubating can may be passed, and clamped down
as in C.

B is fitted with three stout iron legs, which should be
sufficiently long to allow of a small lamp or gas-jet
being placed beneath the container to maintain a uniform
temperature.

D gives an external view of the apparatus.

For the preparation of soured milk, separated milk is
placed in the incubating can, and heated up to 100 deg. C.
(212 deg. F.) for thirty minutes. It is then allowed to cool
to room temperature, and the culture, or tablet containing
the lactic acid bacteria, is then added, and thoroughly
stirred for a minute or so. The can is then immersed in
the warm water container and kept at a temperature of 86 deg.
F. to 104 deg. F., according to the organisms used, for ten to
twelve hours. By the end of this time the milk ought to be
converted to a jelly-like mass, and after being stirred
vigorously for a short time, may be cooled on ice, and is
then ready for consumption.]

The incubating temperature could very conveniently be maintained by an
electric radiator, and as the insulation would largely prevent leakage,
the amount of electric current used would not be large. The regulating
apparatus