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 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° F., Koning[82] found 2.35 per cent. and 2.5 acid; while similar samples stored at 60° to 62° 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° F.; and Jensen states that _Bacillus casei ε_ 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.