Abstract
1. O-fraction obtained from tumor tissue inhibited the growth of E. coli but not of Proteus vulgaris.
2. TO-fraction obtained from tumor tissue did not inhibited either the growth or the synthesis of catalase of E. coli.
3. Various divalent or trivalent cations and RNA or DNA removed the growth inhibiting action of O-fraction.
4. Oxygen consumption of E. coli was inhibited by O-fraction regardless of the kind of added substrate.
5. The inhibition of oxygen consumption was removed by magnesium ion and RNA or DNA.
6. The nature of anti-bacterial principle and its mode of action were discussed.
