250 LECTURES ON IMMUNITY 



antialexin was produced by the injection of the alexin 

 used, which was not the case in the other series. It seems 

 quite possible that this method is the only one adapted to 

 yield a specific antialexin with a strong affinity for the 

 injected alexin. 



If the affinity be not very marked, and therefore the 

 reaction between alexin and antialexin to a high degree 

 incomplete, we would not expect to find a proportionality 

 between the neutralising quantity of antialexin and the 

 quantity of alexin present. (It may be remarked that it 

 is here not a question of an absolute neutralisation, by 

 which the quantity of haemolysin would sink to zero, 

 but only of a reduction of the quantity of haemolysin to 

 about 14 per cent of the value exhibited in the absence 

 of antialexin (cf. p. 229).) 



What complicated phenomena may be encountered in 

 such cases is evident from the following example, in which 

 it is supposed that the formula valid for the equilibrium 

 has the form, (5 a ;r)(2O b x) 100 x> which quite 

 closely corresponds to the combination of the immune-body 

 (a) from a goat treated with bullock erythrocytes and with 

 guinea-pig serum as alexin (b) to haemolysin (;r). I have 

 supposed that an antialexin of the same affinity for the 

 alexin as that of the immune-body is added, so that the 

 same formula may be used for the two cases of equilibrium. 

 From this it follows that the proportions of alexin bound 

 to immune-body and antialexin are identical with the pro- 

 portions of these two substances themselves. The fol- 

 lowing table corresponds directly to those of Morgenroth 

 and Sachs, b is the quantity of alexin necessary for com- 

 plete haemolysis in the presence of the quantity a of im- 



