288 Wassermann Reaction for Diagnosis of Syphilis 



puscle suspension and complement and the paper added i square, 2 squares, 

 2]/^ squares, and so on until the unit is determined. When that is achieved 

 the exact size of the paper containing the unit being known, one sheet of the 

 paper can be ruled into squares of that size or into squares of twice that size — 

 since the "dose" is two units — at the option of the investigator. 



The sheets of paper are kept in a clean envelope, the quantity 

 for each test being cut off as needed. The dry serum changes so 

 little that the dose once determined, the size of the square of paper 

 needed for the test remains about the same. 



The method has the advantage that the amboceptor serum 

 cannot be spoiled or spilled. It has the disadvantage of being 

 slightly less accurate, though it must be admitted that the chances 

 of error in measuring and diluting the fluid serum are probably as 

 great as those arising from inequalities in the distribution of the 

 serum throughout the paper. 



(4) The Antigen. — It has already been shown that complement 

 is labile, and it may have occurred to the reader that its activity 

 is similar to that of ferments. It is now necessary to point out the 

 many conditions (some of which may arise in the performance of 

 a test so delicate as the Wassermann reaction) by which the comple- 

 mentary action may be affected or set aside. Thus, temperature 

 affects it, and temperatures of o°C. suspend it. It is on this ac- 

 count that the test is always made at 37°C. Like most of the 

 ferments of the living organism, salts affect it, and in salt-free media 

 its action ceases, to return when a small quantity of an alkaline salt 

 is added. Not only inorganic salts, but salts of the fatty acids and 

 the bile-salts may inhibit it. Certain lipoids, such as lecithin, 

 cholesterin, protogon and tristearin^ and neutral fats inhibit the 

 complementary action. Some of these substances are always 

 present in the serum containing the complement itself or in the other 

 serums to be tested by its use, and, as Wassermann and Citron have 

 pointed out, we really know nothing about complementary action. 

 Aleuronat, inulin, peptone, albumose, tuberculin, natural and 

 artificial aggressins, gelatin, casein, sitosterin, coagulated serum- 

 albumin, and albuminous precipitates all act as inhibitives to 

 complementary action. 



Now, in all combinations of several serums and antigens it is 

 .always possible that some of these complement-binding or comple- 

 ment-inhibiting substances may be present, hence the first thing that 

 has to be done in the way of titrating the antigen — which is a tissue 

 extract, rich in lipoids which inhibit complementary action — is to 

 determine how much of it can be added to the "hemolytic system" 

 without disturbing hemolysis. 



As, however, the antigen is not used by itself, but always in com- 

 bination with a serum to be tested, we must always combine it with 

 serum when making the titration, so that the requirements of the 

 test may be conformed with. In order that the essential difference 

 between the normal serum and the syphilitic serum can be reduced 



