Tween 80 was investigated for growth-stimulating effect upon Mycobacterium johnei. Modified Ogawa's medium containing the bacillary bodies of M. phlei was used. The growth of M. johnei (two pathogenic strains) was evidently stimulated by Tween 80 at the concentration of 0.5 percent. These results agreed with the previous findings obtained with dysgonic bovine tubercle bacilli. Comparative examination of this and Smith's media revealed that colonies appeared early in Smith's medium, but that no

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... etectable difference was pre-sent in growth after two months' incubation between the two media. Tween 20,40,60, and 80 were examined for growthstimulating effect for M. johnei at the concentration of 0.5 percent. Tween 20 and 40 were less effective than Tween 60 and 80. The growth of M. johnei decreased evidently when M. phlei was added to the medium at the rate of 0.25 percent. No detectable effect was observed when the concentration of glycerin added was decreased to 0.5 percent.