, in other cases
eight to ten hours. Grated nutmeg, ground cinnamon, or other flavouring,
and cream may be used with the soured milk.

The night light is also employed in the "Veronelle" apparatus of Messrs.
Clay, Paget and Company, Limited (Fig. 49).

[Illustration: FIG. 48.--Messrs. Allen & Hanbury's Soured
Milk Apparatus. They maintain the temperature by means of
a night light, and the culture they use they call
"Sauerin."]

[Illustration: FIG. 49.--Vironelle Apparatus for souring
milk, made by Messrs. Clay, Paget & Company, Limited. The
milk in this case is placed in an earthenware jar, and is
sterilised by placing in a saucepan of water and boiling
it. The culture is added after cooling, the period of
incubation being about six hours.]

The containing vessel is of tin or aluminium, and has two stands, the
high one for hot and the low one for cold weather, as in the latter
case greater heat is needed to maintain the incubating temperature. The
milk is placed in an earthenware jar and is sterilised by placing it in
a saucepan of water and boiling it; continuing the boiling for half an
hour. It is allowed to cool to about 98 deg. F., and placed in the
incubator, culture added, and the lamp lighted, the cover of the
incubator being kept on. The period of incubation is given as six hours.
To prepare the next day's supply a tablespoonful of the soured milk is
retained and used instead of the culture. This may be continued for
fourteen days, when a fresh start with culture is necessary. The soured
milk will keep for thirty-six hours. Capacity, one and one half and two
pints; also a large size for family use.

For the preparation of soured milk on a small scale, one of the various
forms of vacuum flasks now on the market may be used with satisfactory
results. A little cold water must be poured into the flasks, and warm
water added, until, by means of three to four changes, boiling water can
be safely poured in without cracking the flask.

This boiling water must be allowed to remain in for about twenty
minutes, and then replaced by freshly boiled milk that has been cooled,
so that its temperature in the flask is about 105 deg. F. The culture of
lactic organisms should then be added, the opening of the flask plugged
with clean cotton-wool, and the cap screwed on.

In an actual test, the temperature of the milk placed in such a flask
was 105 deg. F., at 7.30 P.M., and had dropped to 93 deg. F. by