328 INFECTION AND IMMUNITY 



1. Antiserum, 0.1 + homologous serum .0001 + complement 



2. Antiserum, 0.05 + homologous serum .0001 + complement 



3. Antiserum, 0.02 + homologous serum .0001 + complement 



4. Antiserum, 0.01 + homologous serum .0001 + complement 

 (Antiserum and homologous serum each brought to 1 c.c. volume 



with salt solution.) 



These tubes are incubated for one hour and hemolytic amboceptor 

 and red blood cells are added. The smallest quantity of antiserum 

 which has completely inhibited hemolysis is the "unit," and one and a 

 half to two times this quantity is used for the test. 



5. A solution of the blood spot or other material to be tested pre- 

 pared as for precipitin test. (See page 306.) 



For the actual test the following mixtures are made in a series of 

 tubes, each of which contains : 



1. Complement ) 



I quantity determined by titration. 



2. Antiserum J 



3. Diminishing quantities of the substance in which the antigen is sus- 

 pected, ranging from 0.1 c.c. downward to 0.0001 c.c. 



Salt solution is added as a diluent up to 3 c.c. and the tubes are 

 placed in the incubator or water-bath at 37.5 to 40 C. At the end 

 of this time red blood cells and amboceptor are added as before. 



The tubes are controlled by a series containing all the above ingre- 

 dients except the antiserum. 



SACHS-GEORGI REACTION FOR SYPHILIS* l 



(Direct Precipitation) 



PREPARATION OF EXTRACT. A beef heart is freed from fat and 

 endocardium, cut up finely and ground in a mortar. It is then shaken 

 with 5 volumes of 95 per cent alcohol and a few glass beads in a 

 shaking machine for 5 hours, allowed to stand at room temperature 

 over night, filtered through ordinary filter paper next morning, then 

 placed in the ice-box for at least two days, when it is again filtered 

 through ordinary filter paper, and is now ready for use. It must 

 first be titrated against a standard extract on a number of sera to 

 determine the optimum dilution and cholestermization. For this, the 

 alcoholic extract is diluted with 1, 2, and 3 parts of alcohol, and to 

 fractions of each of these dilutions, 0.3, 0.45, 0.6 and 0.75 per cent of 



* For this description we are indebted to our associate, Dr. Fred 'k. Parker, 

 Jr., who has given particular attention to this reaction. 



