[Some properties of the alpha-hemolysin produced by a hemolytic strain of E. coli]. 
It was found that alpha-hemolysin of E. coli P 678 HIy+ was maximally active against human erythrocytes at pH 6.5.  The hemolytic activity is characterized in time by a distinct lag-phase and a phase of the greatest velocity of the reaction immediately following it.  The duration of the lag-phase and also the rate of hemolysis depends on alpha-hemolysin concentration, whose increase is accompanied by a decrease of the lag-phase and acceleration of hemolysis.  There is a definite limit below which the duration of the lag-phase remains unchanged with further increase of hemolysin concentration.  There was noted a linear relationship between the amount of erythrocytes taken for the test and the rate of hemoglobin release and also a temperature activation of the hemolytic reaction.