184 TECHNIQUE OF THE COMPLEMENT FIXATION METHOD 



found to give absolutely reliable results; i.e., negative reactions with non-luetic 

 bloods, and a high percentage of positive results (almost 100 per cent.) in cases with 

 florid non-treated lues. If the new extract is found to give a negative or weakly posi- 

 tive test while the standard extract shows a strongly positive reaction, it is evident 

 that the dose of the new antigen must be increased; vice versa, if the new extract 

 gives too many positive results especially with sera of known non-luetic origin, the dose 

 should be diminished. (See Table II.) 



From this table it is readily seen that the new extract conforms fully in its results 

 with the standard extract as far as the negative sera and the two strongly positive (2 

 and 9) sera are concerned. In other cases (5, 6 and 10) the new extract gives only par- 

 tial inhibition of hemolysis while with the control antigen complete inhibition results. 

 With sera 3 and 7 there is complete hemolysis instead of partial fixation. These data 

 prove that the new antigen is not sufficiently active in the dose of 0.025; consequently 

 another set of control reactions must be undertaken this time employing 0.05 of the 

 antigen. By thus repeatedly altering the dose cf the antigen, the results will finally 

 tally approximately with the standard extract (rarely do they do so absolutely) and 

 only then may the former be used for the routine examinations. Once the proper 

 dose of this watery extract is established, it remains constant for a very long period. 

 If the strength of the antigen changes at all, it does so, in contrast to the alcoholic 

 extracts of normal organs, only very gradually, and may then have to be used in 

 smaller or greater dosage as determined by renewed tit ration. 



Several sera from cases with high temperatures or scarlet fever should be included 

 among the tests as in these conditions the tendency toward inhibition of hemolysis 

 in the presence of lipoids is increased. 



For the sake of economy, Meier has been working with one-half quantities of all 

 the ingredients; thus 



0.5 c.cm. of the diluted antigen instead of i .o c.cm. 



o.i c.cm. of the diluted serum instead of o. 2 c.cm. 



0.5 c.cm. of the diluted complement instead of i .o c.cm. 



0.5 c.cm. of the diluted hemolysin instead of i .o c.cm. 



0.5 c.cm. of the diluted red cell emulsion. . .instead of i .o c.cm. 



The hemolysin is taken in three to four times its minimum hemolytic dose or titer, 

 as the turbid antigen per se inhibits hemolysis more strongly than the clear extracts. 

 In the hands of an experienced worker, Meier's method undoubtedly yields most 

 reliable results. The author, however, sees no distinct advantage in these modifications. 

 He therefore advises the classical method for the beginner, as it combines simplicity 

 with correctness. 



Citron's Standard for the Strength of a Reaction. 



Citron divides the positive complement fixation tests into four grades, 

 as fellows: 



a. Tubes i and 2 show complete absence of hemol- 



ysis: + + + + 



b. Tube i shows complete absence of hemolysis and 



2 shows faint hemolysis: 



Strongly 

 positive. 



