1. The addition of small amounts of aqueous gentian violet, acriflavine, or acriviolet to suspensions of young cultures of B. anthracis reverses their Gram reaction, and diminishes their diameter about 40 per cent.
2. The time required for these changes varies with the strain of B. anthracis examined.
3. These changes are accompanied by a loss of weight.
4. Ninhydrin-positive substances are demonstrable in the filtrate from suspensions of B. anthracis to which dyes have been added.
5. Similar changes are produced by these dyes in many, but not in all, of the sporogenic aerobes.
6. Non-spore bearers are for the most part unaffected in these ways by the dyes, although to this statement there are a number of exceptions.
7. The change in size produced by the dyes is demonstrable in hanging drop specimens as well as in stained smears, but not with equal constancy.
8. Partial decolorizations of B. anthracis are described, which are produced by modifications of the Burke technic in which time of exposure to dye is shortened and time of exposure to decolorizer lengthened.
9. The explanation for these phenomena which accords with all the known facts is that they depend on the existence in B. anthracis of a Gram-positive cortex and a Gram-negative medulla. Positive proof of the correctness of this explanation must await the evidence furnished by cross-sections of bacteria.