320 



INFECTION AND IMMUNITY 



tion. He calls attention to the experiments of Morgenroth and Sachs 10 

 who have shown that the relationship between complement and ambo- 

 ceptor necessary for hemolytic reactions is one of inverse proportions. 

 In their own words, "in the presence of larger quantities of ambo- 

 ceptor, smaller quantities of complement suffice," and vice versa. 

 Noguchi, in his work, has found that, while in the presence of one 

 unit of amboceptor, 0.1 c.c. of guinea-pig's complement is required to 

 produce hemolysis, by using four, eight, and twenty units of ambo- 

 ceptor, complete hemolysis is obtainable with one-third, one-fifth, and 

 one-tenth of the 0.1 c.c. of complement, respectively. For this reason 

 an excess of amboceptor might result in complete hemolysis in a test, 

 if a small fraction of the complement were left unfixed by the syphil- 

 itic antibody. Another result of an excess of amboceptor would con- 

 sist in a partial dissociation of the complement from its combination 

 with the antigen-antibody compound. As Noguchi puts it, " a quantity 

 of syphilitic antibody just sufficient to fix 0.1 c.c. of the complement 

 against two units of the amboceptor is no longer efficient in holding 

 back the complement from partial liberation against the influence 

 exerted by more than four units of the amboceptor." 



From these considerations it follows that the serum from rabbits 

 immunized against sheep corpuscles must, in each case, be titrated in 

 order to determine the hemolytic unit. For this purpose a number of 

 mixtures are made in test tubes, containing each 0.1 c.c. of complement 

 (fresh guinea-pig serum), 1 c.c. of a 5 per cent emulsion of sheep 's 

 corpuscles, and diminishing quantities of the inactivated hemolytic 

 serum, thus: 



In the given case, 0.001 c.c. of the serum represents one unit, and 

 0.002 c.c., two units, is the quantity to be used for each test. 



16 Morgenroth und Sachs, in Ehrlich's ' ' Gesammelte Arbeiten," etc., Berlin, 

 1904. 



17 In each tube the volume of the mixture should be made up to 5 c.c. with 

 0.85 per cent salt solution. 



