[Illustration: FIG. 24.—Shredded preparation of the Bulgarian original Yoghourt. Stain: aqueous methylene blue. Granule bacillus, diplostreptococci, and yeast. (See also other photo-micrographs of Yoghourt. Enlarged 1:70.)] [Illustration: FIG. 25.—Granule Bacillus from Yoghourt. Cultivated in skim milk in twenty-four hours at 37° C. Stain: aqueous methylene blue. (Enlarged 1:50.) By means of this staining treatment the presence of granules (not spores) can be easily detected. Treatment with fuchsine fails to bring out these formations.] [Illustration: FIG. 26.—_Bacteria W._, Agar Milk Sugar Culture. Cultivated twenty-four hours (knobs, clubs). Stain: Gram's method coloured with aqueous fuchsine afterwards. (Enlarged 1:600.)] [Illustration: FIG. 27.—_Bacteria acidophilus_ from calves' manure, isolated by means of bouillon as acid as vinegar. Shredded out of the usual Agar culture. Twenty-four hours at 37° C. Stain: aqueous methylene blue. (Enlarged 1:700.)] [Illustration: FIG. 28.—Mucus from calf's stomach inoculated into milk after eight transferrings. Shredded preparation cultivated in milk for twenty-four hours at 37° C. Diplostreptococci and granule bacillus. Stain: aqueous methylene blue. (Enlarged 1:500.)] [Illustration: FIG. 29.—Diplostreptococcus from Yoghourt. Pure culture in skim milk. A comparison of the illustrations will show how close a resemblance exists between bacteria found in the mucous membrane of calf's stomach and those occurring in Yoghourt. In fact, by the combined action of granule bacilli, and of diplostreptococci from calf's stomach, together with a Yoghourt yeast, it is possible to prepare normal Yoghourt.] In a review of the literature of the subject of soured milks, Makrinoff suggests the adoption of the two names, _Streptobac. lebenis viscosus_ and _Streptobac. lebenis non-viscosus_, for the organisms of the so-called Bulgaricus group, and known at present as _Bacillus-bulgaricus_, _Streptobac. lebenis_, _Bacillus of Massol_, _Granule bacillus_, _Bact. Mazun_, _Bac. lactis acidi_, etc.[77] White and Avery[78] have made a comparative study of a large number of varieties and species of lactic acid bacteria of the above type obtained from various fermented milks and milk tabloids. Their descriptions are so detailed and their conclusions are so important that we give them at length. According to this work, the whole of the thermophilic lactic acid bacilli of the so-called Bulgaricus type may be divided into two sub-types, A and B. _The Cultural Characteristics of the Bacillus Bulgaricus Group_ The cultural characteristics of all the strains of _Bacillus bulgaricus_ (granule bacillus) are as follows: _In Whey Agar._—All strains exhibit wide variation in size, 2 µ to 50 µ long and about 1 µ broad.