236 LECTURES ON IMMUNITY 



for the alexin. If it be added in small quantity, there 

 cannot be formed more than the equivalent quantity of 

 haemolysin. This property is also very evident from the 

 measurements. 



Much better than all general considerations do the 

 agreements between the values calculated from the for- 

 mula and the observed values indicate the correctness of 

 the view adopted. This formula indicates also that one 

 unit of the haemolysin (that is, the hundredth part of the 

 quantity necessary to haemolyse completely i c.c. of a 

 5 per cent suspension of bovine red blood-corpuscles) is 

 equivalent to the fifth part of a unit of immune-body 

 and to the twentieth part of a unit of alexin. The cir- 

 cumstance that the quantity of haemolysin is to be sub- 

 tracted from the quantity of added immune-body and 

 alexin, recalculated to equivalent quantities, shows that 

 both substances are consumed in the formation of the 

 haemolysin. The form of the equation indicates also 

 that one molecule of immune-body and one molecule of 

 alexin form one molecule of haemolysin. 



Another illustration is red corpuscles from sheep blood 

 attacked by a haemolysin formed of an immune-body from 

 a goat injected with sheep blood, and alexin in serum 

 from guinea-pigs. The quantity of haemolysin, x, was cal- 

 culated with the formula : 



(40 a x) (25 b x)= 1900 x. 



I give only the series for the observed haemolysis. 



The agreement between the observed and calculated 

 values is, as in the preceding illustration, as good as could 

 be desired, that is, within the possible experimental errors. 



