354 STUDIES IN IMMUNITY. 



his last experiments, which show a grave experimental error, are 

 the following: The normal rabbit serum treated with insufficiently 

 washed sheep corpuscles brought about the inhibition of hemolysis 

 already noted, when, for the sensitizing of the test corpuscles, he used 

 S. rabbit > ox, 55 degrees. In this case the excess of sensitizing 

 serum was left with the test corpuscles, and of course a precipitate 

 was formed in the last stage of the experiment, and hemolysis 

 thereby inhibited. No such " anticomplement action" took place 

 if he sensitized the corpuscles both with serum rabbit > ox, 55 

 degrees, and with heated normal rabbit serum. In this instance 

 he removed the excess of both sensitizing sera, and no precipitate 

 was formed. And again he notes that no inhibition of hemolysis 

 occurred if, for sensitizing the test corpuscles, he used normal rabbit 

 serum alone. Incidentally, the serum was removed in this case, 

 but of course no inhibition would have taken place anyway, as no 

 precipitate was formed.* Manifestly, the fixation of alexin (inhibi- 

 tion of hemolysis) occurs only in the presence of a precipitate 

 formed by the interaction of an excess of immune serum and the 

 precipitinogen of the sheep serum carried from the first incom- 

 pletely washed corpuscles. The following experiment comprises a 

 complete refutation of Sachs' hypothesis and puts in evidence the 

 alexin-fixing precipitate : 



EXPERIMENT V. 

 The tubes are prepared as follows: 



Tube A. Sheep corpuscles (washed once) 3 c.c. 



Serum normal rabbit, 55 degrees 3 c.c. 



Tube B. Sheep corpuscles (washed five times) 3 c.c. 



Serum normal rabbit, 55 degrees 3 c.c. 

 Contact, 1 hour at 37 C 



Centrifugalization, and, from the supernatant treated sera A and 

 B, are formed two tubes: 



Tube A 1 . Treated serum "A" 2.5 c.c. 



Alexin guinea-pig 0.25 c.c. 



TubeB 1 . Treated serum " B " 2.5 c.c. 



Alexin guinea-pig 0.25 c.c. 



* Sachs, I.e.; compare Tabelle 2, Kol. I and II; Tabelle 3, Kol. B, and Tabelle 2, 

 Kol. I. 



