254 LECTURES ON IMMUNITY 



certain quantity of antiserum can bind only a given equiv- 

 alent quantity of immune-body, so that erythrocytes pro- 

 tected from haemolysis by the absorption of a certain 

 quantity of antiserum may yet be haemolysed on the further 

 addition of immune-body and alexin. Normal rabbit-serum 

 heated to 56 C. contains a substance which does not act as 

 an immune-body against bovine erythrocytes, but has the 

 faculty of binding antiserum, so that it can produce the 

 haemolysis of erythrocytes that are loaded with the com- 

 pound of immune-body and antiserum. This haemolytic 

 action is weaker if the compound has lain for a long time 

 in the erythrocytes, than if the preparation is fresh. This 

 peculiarity seems to indicate that the compound, just as the 

 analogous haemolytic substances such as tetanolysin and 

 probably also the compound hoemolysins, is slowly bound 

 by the protein substances in the erythrocytes. The normal 

 rabbit serum evidently contains some substance which com- 

 petes with the immune-body in binding antiserum. 



Bordet and Gay made an observation confirming a dis- 

 covery of Klein. 1 The immune-bodies and alexins con- 

 tained in sera are absorbed to a much higher degree by the 

 erythrocrytes if these are suspended in a physiological 

 salt-solution, than if they are suspended in a natural serum. 

 Thus a mixture of 0.4 c.c. of normal horse-serum and 

 0.4 c.c. of erythrocytes from the guinea-pig was treated 

 with i c.c. of ox-serum without showing agglutination of 

 the erythrocytes to a notable degree. If, on the other hand, 

 0.6 c.c. of physiological salt-solution had been present for 

 some time in the said mixture, agglutination was very 

 pronounced. In an analogous manner we may explain an- 



1 Klein: Wientr klin. Wochcnschrift, No. 48 (1905). 



