My attention was first directed to this subject during the course of experimentation on the effect of "Sanocrysin" on the tubercle bacillus.1It was observed that, after a certain time of exposure of apparently pure cultures of tubercle bacilli, various forms of organisms appeared that resembled the tubercle bacillus except they were not acid fast. Furthermore, these organisms were gram negative, motile and grew rapidly. An injection into guinea-pigs caused a peculiar type of pathologic change, that will be reported later.2At first, these organisms were discarded as ordinary contaminations and the work was repeated, other cultures being used, but with the same results. We observed further that besides the "gold" treatment (which consists in suspending a 5 per cent emulsion of bacilli in 1:2,000 "Sanocrysin"), there were other ways of bringing about the same result. One was to grind the organisms in a ball mill for from