162 ANTIGENS AND THE TECHNIC OF SERUM REACTIONS 



After mixing the tubes are placed in a water-bath maintained at 

 37 C. for one hour, to permit of the fixation of complement; 1 c.c. 

 of a 5 per cent, suspension of erythrocytes and two units of hemolysin 

 are then added to each tube, mixed and reincubated for one hour, 

 then read. Tubes 1, 3, 5, 7, 6 and 8 should show complete hemolysis. 

 Tube 4 should show complete inhibition of hemolysis (positive reac- 

 tion) . If such be the case all the reagents are properly adjusted, and 

 Tube 2, containing the unknown serum, is read. If hemolysis is 

 absent the reaction is positive; if hemolysis is complete the reaction 

 is negative. 2 



The Method of Noguchi. 3 A rigorous standardization of reagents 

 is a prerequisite for accuracy in the serum diagnosis of syphilis, and 

 Noguchi has pointed out that a variable inherent inaccuracy exists 

 in the Wassermann method. He has shown that human sera may 

 contain variable amounts of hemolysin specific for sheep erythrocytes. 

 Human sera, however, contain no hemolysin for human erythrocytes. 

 The Noguchi modification, therefore, substitutes human red blood 

 cells (obtained from placenta or at autopsies) for sheep red blood 

 cells. Rabbits are immunized to carefully washed human erythro- 

 cytes and the hemolytic unit of the rabbit serum is determined in the 

 usual manner. The following reagents are required to perform the 

 Noguchi test : 



1. Complement Fresh guinea-pig serum in 40 per cent, dilution 

 (one part clear fresh serum to 2.5 parts sterile salt solution). 



2. Hemolytic Serum Rabbit serum, immunized against human 

 erythrocytes, is titrated against human erythrocytes to determine the 

 hemolytic unit. Two units are used in the test. 



1 Twice the antigen titer, determined by titration, diluted with salt solution; thus, if 

 the antigenic titer of the acetone insoluble extract is 0.2 c.c., and the anticomplementary 

 titer is found to be 1.75 c.c., 0.4 c.c. of the extract are diluted with 0.6 c.c. salt solution 

 and used in the diluted state. In practice, enough extract should be diluted to last one 

 day. 



2 For a discussion of results, see section on Treponema pallidum. 



3 Noguchi, Serum Diagnosis of Syphilis. 



