274 INFECTION AND IMMUNITY 



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

 tubes, each of which contains: 



„' , , . [ quantity determined by titration. 



3. Diminishing quantities of the substance in which the antigen is suspected, 

 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 ingredi- 

 ents except the antiserum. 



