194 THE PRINCIPLES OF IMMUNOLOGY 



been recommended by Shakell, but Karsner and Collins found that the 

 activity was lost in eleven to fifteen days. Moledzky states that com- 

 plement in the frozen states retains its strength indefinitely, but Reu- 

 diger found that although its strength is somewhat augmented at the 

 end of one week, it deteriorates after the second week of preservation. 

 Preservation for even these periods involves a good laboratory equip- 

 ment and considerable skill. Kolmer recommends the addition of 

 chemically pure sodium chloride to pooled guinea-pig sera in the pro- 

 portion of 0.425 gram salt to 10. c.c. serum. This is effective for sev- 

 eral weeks' preservation, and dilution is so adjusted as to restore the 

 serum to practical isotonicity. Detre used rabbit complement, but it is 

 not as desirable as guinea-pig complement and has the same objections. 

 Human complement is employed in several modifications of the Was- 

 sermann test, but is present in human serum in extremely variable 

 amounts and is difficult to titrate. It is, however, easily accessible, 

 as it is present in the serum to be tested for syphilitic amboceptor. 

 The selection of the complement to be used depends to a certain 

 extent upon the hemolytic system and the modification of the test 

 which is employed. 



Complement should be used in accurately-determined amounts. 

 Therefore, titration is of the utmost importance. Guinea-pig serum 

 shows individual variation in complement, but in large laboratories 

 this may be in part overcome by the " pooling " or mixing of the sera 

 from several guinea-pigs. Such pooling, however, does not remove the 

 necessity for titration. In some laboratories the complement is diluted 

 i to 10, and the hemolytic amboceptor titrated each day by testing. 

 We are of the opinion from experience and in view of the work of 

 Sasano that the complement should be titrated in various dilutions 

 (see page 190) against a constant amount of previously titrated hemo- 

 lytic amboceptor. In either case the titration should take place on the 

 same day as the Wassermann tests are made. The use of a single unit 

 of complement does not allow for the presence of anti-lytic bodies in 

 the reagents nor for possible deterioration of complement. At 37 C. 

 the use of one and one-fourth units appears to be most satisfactory, 

 whereas at ice-chest temperature the use of two units appears to be 

 more desirable. Titration of the complement should be most accurate 

 and the end-point be determined only by absolutely complete hemolysis. 



The Hemolytic System. Sheep erythrocytes and the correspond- 

 ing hemolytic immune serum obtained from the rabbit were used by 

 Wassermann and are widely used at the present time. Other systems 

 include the use of goat, horse, ox, human and fowl corpuscles, with 

 specific antisera obtained by immunizing rabbits. Certain investi- 

 gators have depended upon the normal hemolysin for sheep erythro- 

 cytes often found in human serum. This is a variable quantity and 

 almost never very large. Noguchi has summarized the hemolytic sys- 

 tems in a table giving all the essential data (see pages 192, 193). 



The preparation of a hemolytic immune serum has been discussed 

 (see page 117). The preservation of this serum in the moist state is 



