416 SYPHILIS 



its main outlines the technique is exactly the same as that already 

 described. The serum to be tested is heated, to remove comple- 

 ment, and diluted with sterile normal saline solution. A dilution 

 of i : 20 or i : 40 is generally correct, but the point may be deter- 

 mined by preliminary tests with a known syphilitic serum ; and in 

 any case it is an advantage to perform a series of tests with 

 different dilutions, so that a rough idea of the amount of antibody 

 present in the serum may be obtained. This is mixed with an 

 extract of the syphilitic organ (antigen), and some fresh guinea- 

 pig serum (complement) added. The proportions may be i c.c. 

 of diluted serum, 0*1 or 0-2 c.c. of organ extract, and 0*2 c.c. of fresh 

 serum. The whole is incubated for one hour, at the end of which 

 time all the complement will be removed from the fluid if 

 syphilitic antibody is present. Next, corpuscles (e.g., of a sheep or 

 pigeon) are added, together with heated serum from a rabbit 

 which has been injected with the corpuscles in question ; or the 

 corpuscles may previously be sensitized with the inactivated 

 serum, washed, and then added. The whole mixture is then 

 incubated for two hours, with occasional stirring or shaking, 

 and kept some hours in the ice-chest. A positive reaction is 

 shown by the absence of haemolysis. Control tests are also 

 advisable e.g., the corpuscles must be completely dissolved by 

 the heated immune serum and the guinea-pig's serum if the other 

 two ingredients are not added, and there should be no haemolysis 

 if all the substances except the guinea-pig's serum are used. 



Ledingham and Hartoch have shown independently that 

 opsonin is absorbed as well as complement, and this fact may 

 be used as a test of the presence of the reaction. In this case the 

 first part of the test is performed as beforehand the fluid used as 

 the serum in an opsonin estimation, using staphylococci or any 

 other organism, and using as a control guinea-pig serum diluted 

 with normal saline to the same extent as it was in the mixture of 

 organ extract, human serum, and guinea-pig serum. In a positive 

 reaction the phagocytic index in the first preparation will be 

 much below that in the second ; in a negative one they will be 

 equal. 



The exact value of the test is not yet quite definitely settled. 

 It is very rarely present in health, and not common in diseases 

 other than syphilis ; but it does occur, especially in diseases which 

 (like syphilis) are due to animal parasites, such as malaria or 

 trypanosomiasis, and is not uncommon in leprosy and scarlet 



