113 deg. F. contained 0.34 per cent. lactic acid and 0.012 per cent.
alcohol. Luerssen and Kuehn[70] came to the conclusion that yoghourt
contained chiefly a mixture of _Bacillus bulgaricus_, diplostreptococci,
and a "granule" bacillus, so called on account of its granulated
appearance after treatment with methylene blue. According to these
authors, the first two organisms were found in each of eight samples of
maya (young yoghourt) and of yoghourt itself, but the occurrence of the
"granule" bacillus in plate cultures was by no means regular. In
addition, yeasts were found in almost every sample examined, but were
regarded more as accidental infections rather than as essential to the
formation of a typical product. The combined action of the three
organisms already mentioned gave rise to a product closely resembling
normal yoghourt. Piorkowski[71] subjected Bulgarian maya to examination
and associated himself with Metchnikoff[72] in finding three species, a
streptococcus, a diplococcus, and a specific organism to which he gave
the name _Yoghourt bacillus_. Similar results were also obtained by
Grigoroff.[73] Piorkowski's _Yoghourt bacillus_ is similar in form to
_Bacillus subtilis_, but does not sporulate, nor does it liquefy
gelatine. Young individuals are stained by Gram's method; older
individuals are, however, Gram negative. The optimum temperature is 112
deg. F. Kuntze attempted to isolate the organisms mentioned by Luerssen and
Kuehn, and by plate culture procured growth of a spore-forming bacillus
similar to Weigmann's _Bacillus matzoon_. To this organism is attributed
the power to impart a specific taste to the matzoon, but as growth is
comparatively slow, it can only be of significance in determining the
quality of the curd and cheese prepared from this product. Cultures were
also obtained which resembled in general character those of the organism
described by Luerssen and Kuehn as _Bacillus bulgaricus_ and named by
Kuntze _Bacterium W_. Granule formation was transient in this culture,
and the organisms eventually became inactive. Further analysis of maya
gave cultures of the "granule" bacillus, but these passed over from the
type forming irregular colonies (see Figs. 14, 15, 16) to that producing
smooth colonies. Further, although the granule formation persists
largely in milk, the organisms soon revert to the non-granular type if
cultivated on agar. By the use of the Gram-Weigert stain organisms from
a several