1 62 THE TECHNIQUE OF COMPLEMENT FIXATION. 



III. Serum Diagnosis of Syphilis. , 



a. Wassermann's Technique. 



The technique of this reaction as carried out in Wassermann's laboratory 

 is practically identical with that just described for the diagnosis of bacterial 

 infections. The preparation of the antigen varies slightly. 



The liver obtained from a syphilitic fetus is weighed and cut up into fine pieces*. 

 Four times its weight of 1/2 per cent, of carbolic solution in saline is added and the 

 mixture placed into a brown bottle and shaken for twenty-four hours. It is then centrif u 

 galized until the larger liver remnants settle to the bottom and a somewhat turbid 

 fluid remains above. The latter is poured off into a brown bottle and placed into the 

 ice-box. After several days of sedimentation, the fluid assumes a yellowish-brown 

 opalescence and can now be used as a luetic antigen. It should not be exposed to light 

 and heat, should not be shaken, and its contents should not be pipetted off, but care- 

 fully poured off without disturbance to the sediment. 



By titration of the extract, that dose is determined which does not of 

 itself bind complement. Only such extracts are kept which in the dose of 

 0.4 c.c. do not interfere with hemolysis. 



Control tests should also be made to ascertain whether the organ extract 

 has any tendency of its own to hemolyse red blood cells without the presence 

 of complement or hemolysin. 



Not every luetic extract can serve as antigen for complement fixation. 

 During the process of extraction a number of other substances, both normal 

 and pathological, may be drawn from the luetic liver besides that agent 

 necessary for the Wassermann test. These undesired ingredients may 

 interfere with the efficiency of the extract. For this reason a great number 

 of known positive and negative sera should be tested with each new extract, 

 and only if the results are absolutely correct should it be employed as antigen. 



In the early work of Wassermann the antigen was described as deteriorating very 

 easily; its activity would either be entirely destroyed or it would become anticomple- 

 mentary. The author is firmly convinced that these changes are brought about by 

 careless handling of the extract or its exposure to light. If properly taken care of, its 

 activity remains constant. 



From practical experience, it has been found that extracts which must be 

 used in amounts less than o.i c.c. are as a general rule unsatisfactory. 

 Similarly, the luetic sera are most active when doses of 0.2 and o.i c.c. are 

 employed. Amounts greater than 0.2 may result in an unspecific reaction. 

 The most favorable combinations are, 



0.2 c.c. of extract + 0.2 c.c. serum, 

 o.i c.c. of extract + o.i c.c. serum. 



The accompanying table presents the titration of an antigen in detail. 



