It appears, therefore, that the injected animal avoids producing 

 isolysines against the blood corpuscles of the variety to which it 

 belongs. The same phenomenon could be observed after the infusion 

 of mules with mule blood, but it did not take place after the infusion of 

 horses with horse blood. The l)est isolytic sei'irm, for instance, for horse 

 blood was therefore obtained by injecting donkeys or mules witli horse 

 blood. The tables supj)ort this idea, for the haemolytic ijidices were 

 indeed highest of the sera of one donkey, and of mules treatetl with 

 horse blood it was also seen that injection of detibrinated blood provoked 

 a more intensive production of isolysines than serum alone. The l^lood 

 corpuscles are of course the best carriers of haemolytic, i.e. isolytic, 

 antigenes. 



The haemolytic power of a serum is to a great extent not dei^endent 

 on the quantity of blood or serum injected, nor on the number of 

 animals the antigenes were derived from; the number of injections 

 and the total time of hyperimmunisation make no difference. Bleed- 

 ings have apparently no influence on the haemolytic index. 



For the rise of isolysines in an animal it is not necessary that it 

 reacts with hyperthermia on hyperimmunisation. 



Animals Hypeeimmunised by Infusion. 



Hyperimmunisation by infusion was done l)y connecting the 

 jugular vein of the animal which is suffering from liorse-sickness with 

 the corresponding vein of the immune animal which has to be hyper- 

 immunised. This method is simple and expedient, and it was usually 

 continued for six minutes. Measured through a trocar and the pipes 

 in use, about half a litre of blood passed through in a minute. There 

 were usually three infusions made into one animal on two or three 

 succeeding days. 



