78 IMMUNE SERA 



tion was shown by the fact that red blood cells of 

 other animals, rabbits or goats for example, exerted 

 no combining power at all when used instead of 

 the sheep cells in the above experiment. The 

 union of these cells, morever, is such a firm one 

 that repeated washing of the cells with normal salt 

 solution does not break it up. 



So far as concerns the technique of the experi- 

 ments, I should like to observe that the addition 

 of red cells in this as well as in all the following 

 experiments was always in the form of a 5% mix- 

 ture or suspension in 0.85%, i.e., isotonic, salt solu- 

 tion. 



The second important question solved by these 

 authors was this: What relation does the alexin 

 bear to the red cells ? They studied this by means 

 of a series of experiments similar to the preceding. 



Experiment 2. Sheep blood was mixed with 

 normal, i.e. not haemolytic, goat serum. After a 

 time the mixture was centrifuged and the two por- 

 tions tested with substance sensibilatrice to deter- 

 mine the presence of alexin. It was found that in 

 this case the red cells acted quite differently. In 

 direct contrast to their behavior toward the sub- 

 stance sensibilatrice in the first experiment, they 

 now did not combine with even the smallest por- 

 tion of alexin, and remained absolutely unchanged. 



Experiment 3. The third series of experiments 

 was undertaken to show what relations existed 



