Penicillin X

In a recent issue ofScience1it was reported that gonorrhea had been successfully treated with single injections of 100,000 units of commercial penicillin incorporated in a beeswax-peanut oil base. For the past several months we have had an opportunity to investigate the properties of so-called penicillin X,2sometimes referred to as factor X, or allopenicillin. This material was furnished to us by three manufacturers.3A small amount of crystalline penicillin X4was also made available to us. When assayed by the cup-plate method5the potency of crystalline penicillin X is approximately 900 units per milligram, while crystalline penicillin6has a potency of 1,650 units per milligram. In addition, in vitro studies (serial dilution) show that penicillin X is more effective than commercial penicillin against a strain of Klebsiella pneumoniae type A and a strain of Bacillus cereus. No difference in effect could be