The identification of Bacillus anthracis involves its differentiation from other aerobic sporeformers, particularly Bacillus cereus. Smith et al. (1952), in a study of aerobic sporeforming bacteria, concluded that B. anthracis is a pathogenic variety of B. cereus. They also stated that strains of B. anthracis which had lost their virulence could not be differentiated from B. cereus. This apparent relationship between B. anthracis and B. cereus was supported by Brown et al. (1958). Burdon (1956) listed characteristics for the identification of pathogenic strains of B. anthracis, but indicated that attenuated and avirulent strains presented properties closely approaching those of B. cereus. The report which follows presents data showing that the combination of a few simple tests serves to identify both virulent and avirulent strains of B. anthracis and in addition differentiates them from B. cereus, Bacillus cereus var. mycoides, Bacillus thuringiensis, and Bacillus subtilis. Data will be presented to show that pathogenic strains of B. anthracis which lose their pathogenicity remain B. anthracis and can be differentiated from B. cereus and the other sporeformers tested. Such a differentiation is of taxonomic and medical importance. MATERIALS AND METHODS Motility. Motility was determined by inoculating tubes of motility test medium (Difco) to which 0.005 per cent of 2,3, 5-triphenyltetrazolium chloride was added to facilitate reading. Tubes were incubated at 37 C for 48 hr. Motility was indicated by the spreading of growth beyond the line produced by the inoculating needle.

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An alkaline medium (Sabouraud's dextrose or maltose agar of pH 10.5) was found to be selective for dermatophytes in the presence of the rapidly growing saprophytic fungi and has been used to isolate dermatophytes from mixed cultures and leather. Virulent dysentery bacteria are able to grow in media of alkaline pH values, while non-virulent strains of the same microorganisms are inhibited completely or very greatly. It is strongly indicated that pathogenicity may be related to pH tolerance and it is suggested that this relationship may be explained by the presence of a trypsin-like enzyme or enzyme system, while a loss of pathogenicity is associated with a loss or weakening of this enzyme system.