79 



l)iscussion. 



Mule 150. — The serum was more haemolytic for mules than for 

 horses. The haemolytic index for mules decreased in 13^ months to i 

 of the original value ; or perhaps the haemolysines disappeared and arose 

 again after a further injection. They increased even within 1^ months 

 although no injection took place. 



Mule 199. — The serum was more haemolytic for horse blood. The 

 index for mules decreased first and then increased fifteen months after 

 injection. 



Mule 201. — The serum of this mule dissolved blood corpuscles of 

 horses much more energetically than of mules. 



Comparative Table. 



Conclusions. 



1. Of three mules treated with horse blood two gave a serum with 



stronger haemolytic properties for horse than for mule blood, 

 the serum of one of them, however, dissolved mule blood 

 better than horse blood. 



2. The haemolytic properties of the serum of one mule were still 



present fifteen months after the last immunisation, they 

 seemed to vary in strength during this time. 



