62 IMMUNE SERA 



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 hsemolytic serum with sheep blood 

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

 eral 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- 

 sibilatrice, but had left the alexin practically 

 untouched. 



It still remained to show the relation of these 

 two substances to the red cells at higher temper- 

 atures. At 37-4o C., as already mentioned, 

 haemolysis occurs rapidly, beginning usually within 

 fifteen minutes. It was possible, therefore, to 

 leave the cells and serum in contact for not over 

 ten minutes. Then the mixture was centrifuged 

 -as before. The sedimented blood cells mixed with 

 normal salt solution showed haemolysis of a moder- 

 ate degree. The solution became complete when 



