APPLICATION OF COMPLEMENT FIXATION 191 



complementary, but this property can be removed by heating to 56 C. 

 for thirty minutes, and the sera are then satisfactory for use. He 

 maintains that heated glycerolated sera give much stronger positive 

 results than fresh unheated sera and somewhat stronger than fresh 

 heated sera. This method is valuable for preserving known positive 

 and negative sera as controls for the Wassermann test. 



Nature of the Syphilitic Amboceptor. The substance in the blood 

 which acts as amboceptor is apparently closely related to the globulins, 

 especially the euglobulin. Recently, however, Duhot has suggested that 

 the albumin is of importance. Pfeiffer, Kober and Field, as well as 

 Rowe, have shown an increase of globulins in syphilitic blood and 

 spinal fluid. Noguchi has taken advantage of this fact in his butyric 

 acid test of spinal fluid, but diseases other than syphilis may lead to 

 increase of globulins in the spinal fluid. Peritz states that the lipoid 

 content of syphilitic serum is increased, but Bauer and Skutezky found 

 no parallel between lipoid content and Wassermann reaction. Klaus- 

 ner believes that the flocculent precipitate which appears on addition 

 of 0.6 c.c. distilled water to 0.2 c.c. fresh syphilitic serum is due to the 

 high lipoid content of the serum. Weston has found no definite increase 

 of serum cholesterol in late syphilis and no parallelism between the 

 serum cholesterol content and the Wassermann reaction. According 

 to Wells, " a favorite interpretation of the Wassermann reaction, which 

 seems to harmonize with the facts, is that there is a precipitation of 

 serum globulin by the lipoidal colloids of the antigen and adsorption of 

 the complement by this precipitate." This is supported by the work 

 of Jacobsthal who has demonstrated such precipitates by use of the 

 ultra-microscope even when they are invisible to the naked eye. Holker 

 has recently studied the colloidal phenomena and finds that the addi- 

 tion of antigen to syphilitic sera produces a turbidity the curve of 

 which is steeper and higher than with normal sera. He finds that the 

 serum is an emulsoid and the antigen a suspensoid. Salt solution dis- 

 perses the serum and precipitates the antigen, thus increasing the pro- 

 tective state of the serum. Negative sera are much more protective 

 than positive sera in preventing the antigen from being precipitated 

 by salt solution. 



The Complement. As has been pointed out in the general discus- 

 sion of complement, guinea-pig complement is most widely useful in 

 immunological work. It was used by Wassermann in his original test 

 and is extensively employed to-day. From the practical viewpoint it 

 has certain objections. Animals are expensive and for a small number 

 of tests it is undesirable to sacrifice an animal. This objection may 

 be overcome by bleeding from the heart or from an ear vein (Rous), 

 but the technic of both these operations is somewhat difficult. Owing 

 to the lability of complement, it cannot be well preserved and the serum 

 must be used soon after collection. The use of dried complement in 

 filter paper has been abandoned, although such complement papers 

 may be preserved for a few weeks in vacuum desiccators or in tubes 

 containing calcium chloride. Drying in the frozen state in vacuo has 



