208 COLLOIDS IN BIOLOGY AND MEDICINE 



has not yet really been demonstrated that a physical fixation and 

 not an irreversible chemical change occurs in complement fixation. 

 Therefore, in what category complement fixation by means of anti- 

 gen plus immune substance is to be placed, is still an open question. 



Wassermann Reaction. 



Complement fixation is much more obvious in the Wassermann 

 reaction. When A. WASSERMANN began his studies, he started with 

 the assumption that extract of spirochsete (as antigen) -{- luetic 

 serum (as immune substance) must fix complement. It was very soon 

 evident, that spirochaBte extract could be replaced by numerous 

 lipoid suspensions: by lecithin (0. FORGES and MAIER), by sodium 

 glycocholate (LEVADITI and YAMANOUCHI), vaseline (FLEISCHMANN), 

 by sodium oleate (H. SACHS and ALTMANN), sodium palmitate and 

 stearate (P. HESSBERG), potato extract and emulsion of shellac 

 '(MUNK). As ELI AS, 0. NEUBAUER, O. FORGES and SALOMON 

 showed, these hydrophile lipoids give precipitates with the globulin 

 of luetic sera which fix complement. 1 



The parallelism between precipitation reaction and complement 

 fixation is very suggestive of a colloid phenomenon. It would be 

 a convincing proof that complement fixation in the Wassermann 

 reaction was a surface phenomenon, if it could be demonstrated 

 that the reaction did not occur in the absence of a precipitation. 

 This proof I gather from an observation of H. SACHS and P. RONDONI. 

 They found that complement fixation by an alcoholic extract of syph- 

 ilitic livers 2 depended upon the manner of dilution with saline solu- 

 tion; diluting drop by drop, they obtained a fluid which bound 

 complement strongly. If the extract is added rapidly to the saline 

 solution, there occurs a weak complement fixation or none at all. 

 By slowly adding drop by drop we obtain a turbid fluid; by rapid 

 mixing a clear fluid. We have here two fluids, which in their ability 

 to fix complement can be distinguished only by the surfaces of the 

 suspended lipoids. The observation of F. MUNK also confirms this 

 view that only alcoholic or acetone and not ethereal extracts or 

 solutions of the above-mentioned lipoids are suitable for binding of 

 complement. 



1 The observations of these authors are very interesting. They observed that 

 even normal sera give precipitates with the lipoids, but that the range of preci- 

 pitation is much broader with luetic sera and that the complement fixation pre- 

 supposes an optimum mass relationship of lipoid and serum. 



2 Before it was discovered that the above-mentioned lipoids were suitable for 

 Uhe Wassermann reaction, extracts of syphilitic livers were employed. 



