150 BACTERIOLYSINS AND HEMOLYSINS 



remains, there are many 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 numerous. 



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 men- 

 tioned, the red blood cells have 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 hemoglobin than that of the corresponding control, it is evident 

 that some of the erythrocytes were hemolyzed and their hemoglobin set 

 free. If the erythrocytes have collected at the bottom apparently in the 

 same quantity as in the control tube, and form there a large deposit, a trace 

 of hemolys is or almost o would be the terms used in reporting the result. 

 Tube 7 after two hours showed incomplete hemolysis, i.e., compared with 

 control III it was noticeably clearer, but not completely transparent. 

 After twenty-four hours there was a small mass of undissolved red blood 

 cells at the bottom of the test-tube and above it a deep red fluid which was 

 only slightly different from that in the tubes where the erythrocytes were 

 completely dissolved. If this sediment should become so small that on 

 shaking only a cloudy turbidity is produced, the result would correspond 

 to the designations "very small sediment," "occasional erythrocytes at the 

 bottom of the tube," or "almost complete hemolysis." 



In the tubes containing inactive hemolysin without complement (control I, and in 

 complement fixation reactions) hemagglutination can occur because the agglutinins 

 which also exist in the serum remain active. Hemagglutination is recognized by the 

 shaking the sediment: the erythrocytes are not equally distributed, but remain in 

 clumps or strings and soon sink to the bottom again. 



For many purposes it is desirable to titrate the complement 



Titration of content of a serum. The method is the same as that used 



the Comple- in hemolysin titration, with the difference that a fixed amount 



ment. o f hemolysin and varying quantities of complement are 



employed. 



The titer of this complement when employed with a hemolysin of i/'iooo strength 

 and allowed to stay in the incubator for two hours would be 0.04 c.cm. 



The complement content of the serum of a healthy guinea-pig is fairly 

 constant. During illness the titer usually is decreased. Among healthy 

 people the complement titer shows marked individual variations. 



For hemolysis a definite quantitative relationship between hemolysin 

 and complement is necessary. 



