Abstract
(1) The lethal toxin of hemolytic streptococci is resistant to heating at 100°C. for 30 minutes and so relatively heat-stable in the neutrality, while it is labile to heating in the acid reaction or particularly in the alkaline reaction, 'as evidenced by being destroyed by heating to 100°C. for 30 minutes under these conditions. In addition, it seems likely that it is less resistant to heating in the strongly acid than in the weakly acid reaction.
(2) The lethal toxin is a toxin different from hemolysin, leucocidin and fibrinolysin.
(3) It has no close relationship to the skin erythrogenic toxin, although it can provoke a slight skin reaction in rabbits.
(4) It possesses a slightly virulence-enhacing action, but the substance which mainly acts as an aggressin is A. P. F. (acid precipitable fraction-bacterial protein) rather than the lethal toxin itself.
In conclusion, I wish to thank Prof. M. Kuroya for much helpful advice and criticism given in the course of this work.
