The strength of guinea pigs complement varies greatly. There are in general two different methods employed by different workers to compensate for this varying potency in determining doses of complement and amboceptor for use in the Wassermann reaction as well as in complement fixation with bacterial antigens. These methods are (1) keeping the dose of complement constant and varying the dose of amboceptor from day to day according to the varying strength of the complement, and (2) keeping the dose of amboceptor constant and varying the dose of complement from day to day according to its varying strength. The fact does not seem to have been recognized that these two procedures represent entirely different things and produce different results.
None of the authors gives any reason for adopting the one or the other procedure.