HMMOLYSINS. 13 



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 

 between the blood-cells on the one hand and the 

 substance sensibilatrice and the alexin on the 

 other, when both were present at the same time, 

 and not, as in the other experiments, when they 

 were present separately. This investigation was 

 complicated by the fact that the specific immune 

 serum very rapidly dissolves the red cells for which 

 it is specific, and that any prolonged contact be- 

 tween the cells and the serum, in order to effect 

 binding of the substance sensibilatrice, is out of 

 the ~ question. Ehrlich and Morgenroth found that 

 at o C. no solution of the red cells by the haemo- 

 lytic serum takes place. They therefore mixed some 

 of their specific haemolytic serum with sheep 

 blood-cells, and kept this mixture at o-3 C. for 

 several hours. No solution took place. They now 

 centrifuged and tested both the sedimented red 

 cells and the clear supernatant serum. It was 

 found that at the temperature o-3 C. the red 

 cells had combined with all of the substance sen- 



