r growth is 113 deg. to
115 deg. F.; growth is fair at 85 deg. F., slight at 75 deg. F., and does
not take place at 68 deg. F.

Colonies on whey agar are round to irregular, greyish white, curled and
filamentous, often streaming, and in a few cases smooth and even in
structure. Gelatine is not liquefied. There is no surface growth on
gelatine stab-cultures. Along the stab the growth is filiform, beaded,
with subsequent horizontally projecting ramifications. Milk is
coagulated in eight to eighteen hours at 112 deg. F., and is the most
favourable medium for growth.

[I am indebted for this group of illustrations (seventeen in number) to
the editor of _Bacteriotherapy,_ New York, U.S.A.--L.M.D.]

[Illustration: FIG. 30--Photo micrograph of preparation
made from Yoghourt, showing yeast cells, large lactic
diplococci, small slender bacilli and many large bacilli
possessing the morphology of _Bacillus bulgaricus_. Yeast
cells are almost invariably found in native Yoghourt, but
do not appear to be essential to the production of a
tropical beverage. Indeed, they would seem to be
responsible for the unpleasant astringent taste often met
with in old samples of this product.]

[Illustration: FIG. 31--Photo micrograph of smear from
Greek Curdled Milk called "Giaourti," and showing yeast
cells, long bacilli and a mould (_Oidium lactis_),
possessing very large elongate cells. The presence of the
latter is very undesirable, as it rapidly combusts the
lactic acid, digests the casein, and imparts a strong
unpleasant cheesy flavour to the beverage.]

Type A produces 2.7 per cent. to 3.7 per cent. inactive lactic acid in
milk, while type B produces only 1.2 per cent. to 1.6 per cent.
laevo-rotatory lactic acid in milk. There is a small quantity of acetic,
formic, and succinic acids formed. The conclusions of White and Avery
are:

I. A review of the morphological culture and biochemical features of the
lactic acid producing bacilli from yoghourt, matzoon, and leben, appears
to justify their classification as a single group.

II. This group would seem to be identical with _Bacterium caucasicum_
(Kern).

III. The significant variations exhibited by these bacilli in regard to
the presence or absence of granules demonstrable by differential stains,
the degree of lactic acid production, and the nature of the acid
produced, suggest a division into two different types--the true type A,
and the paratype