SYPHILIS 



127 



will enable you to measm'e I or 4 units of any fluid quickly 

 and accurately. 



The Process. Take i unit of the serum to be tested and 4 

 units of normal saline solution and mix them in a small test- 

 tube. This is the control, to see whether there is sufficient 

 complement for the test, as is practically always the case with 

 fresh serum. 



Take I unit of the serum and 4 units of the antigen, diluted 

 i in 10, and mix. This is the actual test. 



Incubate five minutes or more in the water-bath at 37 C, 

 or fifteen minutes or more in the ordinary incubator. 



Now add i volume of washed corpuscles and i volume of 

 amboceptor serum. After a few minutes, stir by sucking the 

 mixture into the pipette and expelling it again once or twice. 



FIG. 25. OPSONIC INCUBATOR MODIFIED TO SERVE FOR THE WASSERMANN 



REACTION ALSO. 



If the corpuscles in any tube are not practically completely 

 dissolved, repeat this process after a few. minutes more. Allow 

 to settle, and read off the result. 



In a negative test there will be complete, or almost com- 

 plete, haemolysis in both tubes. 



In a positive test there will be complete, or almost com- 

 plete, haemolysis in the first tube, and no haemolysis in the 

 second. 



One of the advantages of this method is that there is very 

 little likelihood of technical error, the process being so 

 simple; the only fallacies likely to arise are from the use of 



