In the practical performance of the Wassermann reaction the doses of all the ingredients have to be adjusted to each other. The original Wassermann reaction and many of its modifications follow the principle of employing a fixed dose of complement and as large a dose of antigen as possible without danger of non-specific fixation. Usually those who follow this method also determine the least amount of antigen capable of giving a positive reaction with positive serum (the antigenic unit). They require that the dose actually used shall be a considerable multiple of this unit and state that the more multiples of the smallest antigenic unit contained in the dose used, the better the antigen.
On the other hand there are many authors, such as Browning and McKenzie, Thomas and Ivy, Thomsen, Boas, Stern, who use an arbitrary fixed dose of antigen and adjust the complement to the dose of antigen in such a way that the complement is capable of giving complete hemolysis in the presence of the dose of antigen used.