lOO CLINICAL BACTERIOLOGY AND H^EMATOLOGY 



Experiment 2 Mix together i volume of fresh serum from an 



active case of syphilis, untreated, and preferably in the secondary 

 stage, and 4 volumes of the diluted antigen. Incubate as before, 

 and again add immune serum and emulsion of red corpuscles. 



Result. — No haemolysis. 



Explanation. — This is a positive Wassermann reaction, and in 

 it the complement has been absorbed, or has disappeared, when 

 incubated in contact with the emulsion of liquids. Of course, 

 in actual practice a control test, using normal saline solution 

 instead of diluted antigen, is necessary to show that the serum 

 contained complement to commence with. This is practically 

 always the case with fresh serum. 



This is an example of the Wassermann reaction in its simplest 

 form. In the practical application of the test there are several 

 considerations to be borne in mind, and there are numerous 

 methods in use. In the original or classical method the serum 

 to be tested is first heated to destroy complement, and then a 

 certain small amount of guinea-pig serum, which contains com- 

 plement, is added. The mixture with diluted antigen is made 

 much as before, and the whole incubated one hour or more. 

 Then heated serum from a rabbit which has been injected with 

 sheep's corpuscles (anti-sheep serum) is added, and, lastly, an 

 emulsion of sheep corpuscles, washed by repeated centrifuga- 

 lizations from normal saline, is added, stirred in, and again 

 incubated. Then again, in a positive test, the complement is 

 absorbed, and the corpuscles are not dissolved, whereas in a 

 negative one solution takes place. We need not discuss this 

 method here at length. I believe its alleged advantages are 

 entirely fictitious,* and in any case it is a process for the expert. 



Of the numerous modifications of the process which have been 

 introduced we shall describe two, which are not beyond the 

 power of an enthusiastic practitioner to repeat, and which give 

 excellent results. 



Author's Modification of the Wassermann Reaction. 



Collection of Blood. — The specimen to be examined should be 

 collected in a Wright's curved pipette in the manner already 

 described. A fair-sized sample (10 to 20 drops) is advisable. If 



* This question was discussed in the author's Hunterian Lectures (Lancet), 

 March 4, 1911, vol. i., p. 564. 



