THE AGGLUTINATION REACTION 



285 



3. Place 1 c.c. of the serum from tube 1 into tube 2. Mix well, and 

 place 1 c.c. of the mixture from tube 2 into tube 3, and so on. When the 

 sixth tube has been reached, discard 1 c.c., as no serum is to be added to 

 the seventh tube, which is the culture control; i. e., it will contain salt 

 solution plus bacterial emulsion. 



4. Add 1 c.c. of bacterial emulsion to each tube, which doubles the 

 serum dilution in each. Tube 1 now contains a serum in a dilution of 





FIG. 82. MACROSCOPIC AGGLUTINATION REACTION. 



Serum of a person who had received three injections of typhoid vaccine. This 

 drawing was made twenty-four hours after the test was set up. The dilutions are 

 marked on the tubes. 



1:20, acting on the bacteria; tube 2, one of 1:40; tube 3, one of 

 1:80; tube 4, one of 1:160; tube 5, one of 1:320; tube g, one of 

 1 : 640. Tube 7, as just stated, contains the bacterial emulsion in salt 

 solution and is the culture control. 



In determining the agglutination titer of a highly immune serum, 

 these dilutions may be continued to any degree. 



5. On each tube the final dilution is marked with a wax pencil. 



