i 3 6 



BACTERIOLYSINS AND HEMOLYSINS. 



in a few moments, others require two hours. The author has made it a 

 rule to read the result after two hours observation, but he notes the progress 

 of the reaction every one-half hour in order to determine whether it is a 

 slowly or rapidly acting hemolysin. 



The following chart demonstrates the titration of a hemolysin as a preliminary 

 experiment to the complement fixation method. 



Determining the end reaction is a source of difficulty for the beginner. 

 Between the extreme "o" i.e., entire absence of hemolysis, where the 

 appearance of the tube corresponds to that of control III representing a 

 suspension of red blood cells diluted with isotonic saline and the other 

 extreme "complete," i.e., complete hemolysis, where every trace of cor- 

 puscular elements has disappeared and a fluid looking like dilute red-wine 

 remains, there are numerous intermediate stages. These intervening 

 grades of reaction are represented by the terms almost o, incomplete, 

 almost complete, and similar expressions. The meaning of the terms is 

 self-evident. How any particular tube is to be designated is of course a 

 subjective question since the so-called transitional stages are so large in 

 number. 



A few hours after the reaction is ended, a remarkable difference may be 

 noted between the tubes in which hemolysis has occurred and those in which 

 hemolysis has been incomplete or totally absent. In the last mentioned, 

 the red blood cells had sunk to the bottom and above them remains a clear 

 fluid which consists of pure saline or diluted serum (complement + immune 

 serum) and is colored accordingly. If the supernatant fluid is richer in he mo- 

 globin than that of the corresponding control, it is evident that some of the 

 erythrocytes were hemolysed and their hemoglobin set free. If the erythro- 

 cytes have collected at the bottom apparently in the same quantity as in the 



