244 INFECTION AND IMMUNITY 



Filtration of Immune Body and Complement. — Muir and Browning 

 have recently shown that, on the filtration of serum, amboceptor or 

 immune body will pass through the filter, whereas alexin or comple- 

 ment is held back. The amboceptor filters equally well, whether or 

 not mixed with the complement. 



The Fixation of Complement by Precipitates. — It has been found by 

 Gengou * and confirmed by Gay ^ and others, that when the serum of an 

 animal immunized with the serum of another species or with a foreign 

 albumin is mixed with a solution of the substance used in the immu- 

 nization, the precipitate formed will remove complement from the mix- 

 ture. In other words, precipitates formed by the reaction of precipitin 

 with its antigen will fix complement. This phenomenon is of great im- 

 portance in complement-fixation tests such as those of Wassermann or 

 Noguchi (see below); for because of insufficient washing, the blood 

 cells used in producing the hemolytic amboceptor, may, from the 

 presence of serum, give rise to a precipitin as well as a hemolysin. 

 In the test done subsequently, a precipitin reacion may take place 

 and by thus removing complement may give a false result. The ab- 

 sorption of complement by such precipitates takes place when the two 

 reacting factors, the precipitin and its antigen, are in extremely high 

 dilution — in fact, when a visible precipitate can not be observed. 



Quantitative Relationship Between Amboceptor and Complement.— 

 Morgenroth and Sachs,' in studying the quantitative relationship ex- 

 isting between hemolytic amboceptor and its complement, have suc- 

 ceeded in showing that within certain limits an inverse relationship 

 exists between these two bodies. If for a given quantity of red blood cells 

 a certain quantity of amboceptor and complement suffices to produce 

 complete hemolysis, reduction of either the complement or the ambo- 

 ceptor necessitates an increase of the other factor. As amboceptor is 

 increased, in other words, complement may be reduced and vice versa. 

 This result is of great importance in arguing against the original con- 

 ception of Ehrlich in supposing these substances to act together mul- 

 tiple for multiple as do compounds in chemical reactions. 



Deviation of the Complement (Complement-Ablenkung) . — It was no- 

 ticed by Neisser and Wechsberg * that in mixing together bacteria, 



1 Gengou, Ann. Past., 1902. 



2 Oay, Cent. f. Bakt., I, xxix, 1905. 



^Morgenroth und Sachs, " Gesammel. Arb. fiir Immunitatsforschung. " Berlin, 

 Hirschwald, 1904. 



■• Neisser und Wechsberg, Munch, med. Woch., xviii, 1901. 



