Abstract
SUMMARY: The amount of haemolysin produced by Escherichia coli grown under various gas phases was determined by the amount of growth obtained under these conditions. Calcium or strontium was required for activation of haemolysin. The haemolytic reaction was stopped by sodium citrate. The loss of haemolytic activity after incubation with trypsin and chymotrypsin indicated that at least the active group of the haemolytic molecule is protein or a peptide.