CYTOLYSINS 135 



that it is inactivated by heating to 55 C. Reactivation by fresh dog 

 serum was undesirable because of the normal amboceptor present. 

 Therefore, they employed fresh guinea-pig serum in fairly large doses 

 and reactivated the heated dog serum so that complete hemolysis oc- 

 curred. Thus they demonstrated the double nature of the normal 

 hemolysins and also that a complement may serve to hemolyze cells 

 of the same species from which the complement is obtained. Other 

 experiments have shown, however, that a complement operates less 

 actively against homologous cells than against heterologous cells. Ehr- 

 lich and Morgenroth. showed similar relationships by employing as the 

 amboceptor normal calf serum and normal sheep serum, as well as 

 similar hemolytic complexes with sheep and goat blood. They also 

 showed that in a number of instances the amboceptor could be dif- 

 ferentially absorbed by cells at o C., leaving complement free in the 

 serum. Such absorption could not be accomplished with all normal 

 hemolytic sera; in some the cells absorbed both amboceptor and com- 

 plement, whereas in others no absorption whatever occurred. They 

 interpreted the absorption of both bodies as due to the possession on the 

 part of the amboceptor of equal avidity of both the cytophile and com- 

 plementophile group, whereas failure of absorption was supposed to be 

 due to a stronger affinity of complement for amboceptor than of cells 

 for amboceptor. We record the fact without accepting the explanation, 

 but it is important that in some instances normal hemolytic sera may 

 fail to exhibit a separability of complement and amboceptor by means 

 of differential absorption. 



A normal serum may be hemolytic for cells of more than one species ; 

 this is true of goat serum, which is hemolytic for both guinea-pig and 

 rabbit cells. In such cases it is possible to absorb one amboceptor, leave 

 the other active in the serum and thus demonstrate multiplicity of 

 specific amboceptors in a serum. Ehrlich and Morgenroth also main- 

 tained that in the case of goat blood there is a different complement for 

 the two types of cells, but as has been indicated in discussing comple- 

 ment this possibility seems unlikely. 



Proportions of Amboceptor and Complement in Normal 

 Hemolysins. Further difference between a normal and immune 

 hemolytic serum lies in the different proportion of amboceptor and 

 complement. In a normal hemolytic serum the amount of amboceptor 

 present is small and the complement is usually present in at least suf- 

 ficient quantity to saturate the amboceptor ; it may be present in excess. 

 In immune sera the amboceptor is increased enormously, whereas the 

 complement is not altered in quantity. Therefore, such an immune 

 serum may contain amboceptor in greater quantities than can be sat- 

 urated by complement and for its full activity requires more com- 

 plement than can be furnished in the immune animal's serum. This 

 increase in amboceptor is out of all proportion to the amount of antigenic 

 cells injected. Muir, for example, calculated that in immunizing a 

 rabbit the total amount of ox blood injected was 30 c.c., and hemolytic 

 amboceptor was produced sufficient to dissolve the erythrocytes in 



