348 STUDIES IN IMMUNITY. 



duces no effect. If 2 c.c. of fresh blood of the rabbit is washed in 

 20 c.c. of salt solution, the water of washing, removed after cen- 

 trifugalizing, gives an immediate serum reaction with the mastic. 

 If the corpuscles are washed a second time with a fresh amount of 

 physiological solution and centrifugalized, the supernatant fluid 

 gives a like reaction. Even the third water of washing gives a 

 positive result with the mastic emulsion. The fourth wash water 

 usually shows no evidence of the presence of serum. 



It is evident from these preliminary observations that enough pre- 

 cipitinogen is present in the diluted serum which surrounds blood 

 corpuscles washed in the ordinary manner, to give a precipitate in 

 the presence of immune serum. Let us now consider more closely 

 the power of this specific serum precipitate to fix alexin. The work 

 of Gengou* demonstrated that a serum active against a foreign serum 

 will, when mixed with this causative albuminoid, absorb alexin, as 

 shown by the absence of hemolysis in sensitized corpuscles sub- 

 sequently added. And the author notes particularly that this 

 absorption of alexin is in proportion to the presence of specific 

 serum precipitates; but he did not determine whether it is the 

 precipitate itself or some other albuminoid in solution that exer- 

 cises this alexin-fixing property. In the light of the present com- 

 munication it is evident that it is the precipitate itself that fixes 

 the alexin. 



The following experiment shows that a specific serum precipitate 

 will fix alexin. To furnish the precipitinogen necessary for the for- 

 mation of this precipitate I have used, instead of dilute separated 

 serum, the supernatant salt solution that had been employed to 

 wash native blood. Such a serum dilution furnishes the same 

 conditions as are obtained when insufficiently washed corpuscles 

 are mixed with the immune serum. 



EXPERIMENT I. 



To 2 c.c. of fresh ox blood is added 38 c.c. of salt solution of 0.85 

 per cent; the suspension is then centrifugalized and the supernatant 

 washing solution removed. The blood is washed with another 38 

 c.c. of the physiological solution and both the washing fluids are 

 used for the following experiment: 



* Gengou, 1. c. 



