Abstract
Many of the methods for penicillin assay were devised and used primarily for testing solutions during the production of penicillin and are not easily applicable to the determination of titers of body fluids in patients under treatment. These have been reviewed by Foster and Woodruff,1 the classic test of Florey2 being in most common use. Of the studies made on body fluids, the method described by Rammelkamp3 involving the use of serial broth dilutions and a strain of hemolytic streptococcus was used by Rammelkamp and Keefer.4 Rosenberg and Sylvester5 have used Foster's method6 of serial broth dilution with Staphylococcus aureus and turbidimetric measurements, while Romansky and Rittman7 have used a method described by Rake and Jones8 based on the property of the inhibition of hemolysin production of streptococci by penicillin. The procedure to be described here is believed to be simpler than