B.

Quite recently Hastings and Hammer[79] recorded the isolation from milk
of an organism producing more acid than either _Bacterium coli commune_
or _Bacillus lactis acidi_. It is characterised by possessing a high
optimum temperature, and by the limited conditions under which it grows
on nutrient media. On this account these investigators suppose it to be
related to those described in the paragraphs on fermented milks, leben,
matzoon, etc., and which are regarded by Kuntze as being identical.

Similarly Boutroux[80] found 1.5 per cent. acidity produced in a
solution containing albuminous matter and glucose; while Richet[81]
states that with the addition of gastric juice to milk as much as four
per cent. acidity may be formed. After storing samples of milk for eight
days at 100 deg. F., Koning[82] found 2.35 per cent. and 2.5 acid; while
similar samples stored at 60 deg. to 62 deg. F. for the same period only
developed 0.9 per cent. Heinemann[83] records the production of 3.0 per
cent. acid in milk incubated at 100 deg. F.; and Jensen states that
_Bacillus casei [Greek: e]_ is capable of developing 2.7 per cent.
lactic acid.

Dr. H. B. Hutchinson, bacteriologist at Rothamsted Experimental Station,
has also been successful in isolating a bacillus from English market
milk resembling in every particular those classified by White and Avery
as type A.

[Illustration: FIG. 32 is a photo-micrograph of soured
milk inoculated with a tablet containing viable and pure
cultures of _Bacillus bulgaricus_, and incubated for
seventy-two hours. These tablets constitute a valuable
means of preparing soured milk for therapeutic purposes.]

[Illustration: FIG. 33 is a photo-micrograph of milk
inoculated with a ferment tablet in which _Bacillus
bulgaricus_ is no longer viable, and the only growth
obtained is that of an organism allied to the _Bacillus
subtilis_ (Hay bacillus) group. Such milk would be
absolutely without value.]

It will thus be seen that organisms related to those of Oriental and
Occidental milk beverages are present in conditions where it is
impossible for them to attain to any active growth. The same class of
organism has also been found in many cases in butter and cheese
throughout the United States.

Of recent years the consumption of milk fermented by these organisms has
been introduced more or less successfully into all European countries.
This custom is due, as we have seen,[84] to