328 Wassermann Reaction for Diagnosis of Syphilis 



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 com- 

 plement 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 complementary action 

 may be affected or set aside. Thus, temperature affects it, 

 and temperatures of o C. suspend it. It is on this account 

 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 

 complement-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 in- 

 hibit 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 combination 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 



