8X 



Discussion. 



Mule' 320. — Tlie blood dissolving properties of this serum were 

 stronger for mule than for horse blood. Notwithstanding two further 

 injections, the haemolytic index fell within five months. Serum 539 

 was already haemolytic before the hyperimmunisations were started. 

 After eight injections the serum was. more destructive to horse than to 

 mule erythrocytes. 



Sera 552 and 573 also dissolved mule blood cells before the immuni- 

 sation, afterwards the isolysines increased, acting more energetically 

 on mule than horse blood. 



Gomparative Table. 



539, 552, and 573. were injected with the blood of the same mules and on the same dates. 



Conclusions. 



1. Three of the mules injected with mule blood had a serum more 



haemolytic for mule than for horse blood. 



2. The sera of three mules dissolved mule blood before hyper- 



immunisation. These isolysines were probably provoked by 

 the previous serum and virus injection. 



