HMMOLYSINS. II 



pend ? Ehrlich was led to these researches partic- 

 ularly by his so-called Side-chain Theory, which 

 we shall examine in a moment. 



He made his experiments with a haemolytic 

 serum that had been derived from a goat treated 

 with the red cells of a sheep. This serum, there- 

 fore, was haemolytic specifically for sheep blood- 

 cells; i.e., it had increased solvent properties ex- 

 clusively for sheep blood-cells. 



Basing his reasoning on his side-chain theory, 

 Ehrlich argued as follows: "If the hsemolysin is 

 able to exert a specific solvent action on sheep 

 blood-cells, then either of its two factors, the sub- 

 stance sensibilatrice of Bordet or the alexin of nor- 

 mal serum, must possess a specific affinity for these 

 red cells. It must be possible to show this experi- 

 mentally." Such in fact is the case, and the ex- 

 periments devised by him are as follows: 



Experiment i. Ehrlich and Morgenroth, as al- 

 ready said, experimented with a serum that was 

 specifically haemolytic for sheep blood-cells. They 

 made this inactive by heating to 55 C., so that 

 then it contained only the substance sensibilatrice. 

 Next they added a sufficient quantity of sheep 

 red cells, and after a time centrifuged the mixture. 

 They were now able to show that the red cells had 

 combined with all the substance sensibilatrice, and 

 that the supernatant clear liquid was free from the 

 same. In order to prove that such was the case 

 they proceeded thus: To some of the clear centri- 



