SYPHILIS lOI 



an incubator is at hand, it is a good plan to incubate the specimen 

 for half an hour or so to insure good coagulation and a good 

 retraction of the clot, as by this means a good crop of serum is 

 secured. Then centrifugalize a short time to throw down the 

 clot and insure clear serum. 



Preparation of the Antigen. — This is prepared and diluted as 

 already described. It is, however, necessary to test it before use, 

 as not all samples are equally potent. The testing is carried out 

 as follows : Obtain half a dozen specimens of serum from normal 

 persons in whom there is no suspicion of syphilis. These must 

 be quite fresh — i.e., not more than twenty-four hours old. With 

 each specimen make the following two preparations in small test- 

 tubes — {a) I part of serum -f 4 parts of normal saline solution ; 

 {h) I part of serum -f 4 parts of the antigen to be tested (diluted 

 I in 10). Incubate for five minutes in a water-bath at 37° C, or 

 for a quarter of an hour in the ordinary incubator. Now add 

 I part of a mixture of one part of washed human corpuscles + 

 4 parts of serum from a rabbit immunized to human corpuscles. 

 Stir once or twice with the pipette, sucking the fluid up and 

 expelling it again, and allowing the mixture to stand. The red 

 corpuscles in [a) should be almost or quite dissolved* the pro- 

 portions are arranged so that there is sufficient complement to 

 effect this, provided there is sufficient amboceptor fully to sensitize 

 the corpuscles. In the {h) tube there should not be quite so much 

 haemolysis — at any rate, not in all the tubes, if several specimens 

 of normal blood are examined. In other words, the antigen should 

 be of sufficient strength to cause slight inhibition of hemolysis with a 

 normal specimen of blood. 



The antigen should now be tested with a specimen of syphilitic 

 blood. The {a) tube should show complete, or almost complete, 

 haemolysis, as before, but there should be none whatever in the 

 [b) tube ; the corpuscles should sink down, leaving a clear, colour- 

 less, supernatant fluid. 



If these two criteria are present, the antigen is fit to use. If 

 not, the best plan is to discard it and prepare fresh. It is highly 

 advisable that the antigen should also be examined from time 

 to time, as it occasionally undergoes rapid changes in strength. 

 It is for this reason that I think no practitioner should be 

 recommended to undertake the test unless he is likely to 

 have it to do frequently. The actual manipulation of the 

 reaction is simple and easily learnt, whereas the testing and 



