The bacteriolytic action of the sera of typhoid patients has been studied extensively by two methods: first, by determining the greatest dilution of the serum that will kill a given dose of typhoid bacilli and secondly, by determining the greatest dilution of the serum that, with the addition of rabbit or guinea pig complement, will kill a given dose of typhoid bacilli. By both of these methods the titers of the patients' sera were found to be higher than those of normal human sera; with the addition of complement the patients' sera sometimes killed typhoid bacilli at a dilution of 1/500,000 or even 1/1,000,000. Korte and Steinberg (1) say that the (bacteriolytic) amboceptor content of the serum rises during the first weeks of the disease and falls towards convalescence. Denison (2) obtained similar results. The latter found that complement remains constant throughout the disease no matter what spectacular increase or decrease the immune bodies might show.