[Illustration: FIG. 15.—Granule Bacillus from Yoghourt, cultivated after the usual Agar method, for twenty-four hours at 37° C. Stain: aqueous methylene blue. (Enlarged 1:500.)] [Illustration: FIG. 16.—Granule Bacillus from Yoghourt. Agar Milk Sugar Culture cultivated for forty-eight hours at 37° C. Below is the true branching, above, the distorted involution form. This production of involution forms occurs chiefly in old cultures, and is an indication of degeneration. Stain: aqueous methylene blue. (Enlarged 1:700.)] [Illustration: FIG. 17.—_Bacteria W._ from Milk, cultivated twenty-four hours at 37° C. Methylene blue. (Enlarged 1:500.) The similarity in the pictures ought to serve as a proof of the near relation of the granule form and non-granule varieties.] [Illustration: FIG. 18.—Agar Milk Sugar Culture. From the original Bulgarian Yoghourt. In the centre, and beneath, the characteristic hairy irregular colonies of the granule bacillus (_Bacillus bulgaricus_ group), to the left, the smooth contoured yeast colonies. The colonies of the former organism always remain microscopic in size. (Incubated several days at 20° to 25° C. Magnified X 10.)] [Illustration: FIG. 19.—Agar Milk Sugar Culture. Surface colony of granule bacillus from calf's stomach. The great resemblance this colony bears to those formed by the granule bacillus from Yoghourt will be apparent. This fact, as well as close agreement in other cultured features, induced Kuntze to place these organisms in one group. (Incubated two days at 37° C. Magnified X 100.)] [Illustration: FIG. 20.—Agar Milk Sugar Culture. Deep-lying colony of granule bacillus from calf's stomach. The form of the colony is often determined by the relative presence or absence of air. (Two days at 37° C. Enlarged about 1:50.)] [Illustration: FIG. 21.—Agar Milk Sugar. Colony of _Bacterium W._ from Yoghourt (non-granular variety of the granule bacteria, as far as possible identical with Luersen and Kühn's _Bacillus bulgaricus_), of a cubical branching-out form. According to Kuntze, the granule formation of this and related organisms is variable, while White and Avery regard it as a constant characteristic. (Incubated two days at 37° C. Magnified x 50.)] [Illustration: FIG. 22.—Two colonies of _Bacillus acidophilus_ from calf's manure. Agar Milk Sugar Culture. With this organism, also, we have conformation to one type of colony, while, in other respects, temperature requirements and production, etc., we have close agreement with the granule bacillus (_Bacillus bulgaricus_). (Two days at 37° C. Enlarged about 1:50.)] [Illustration: FIG. 23.—Beer-wort Gelatine. Fourteen-days-old colony of Yoghourt yeast. (Enlarged about 1:50.)]