286 STUDIES IN IMMUNITY. 



amount of non-sensitized corpuscles (i.e., treated with normal rabbit 

 serum, 56 degrees, and then washed) loses no antisensitizing power. 



(C) Does the antiserum neutralize the sensitizer directly, like a 

 true antitoxin, or does it simply neutralize the effect of this sub- 

 stance in some antagonistic manner? To answer this question we 

 must determine whether corpuscles sensitized and then cured by 

 antiserum remain refractory to alexin even after being washed in 

 salt solution. 



Experimentally, we find that they do. We add to 0.1 of a cubic 

 centimeter of sensitized blood 0.3 of a cubic centimeter of anti- 

 serum; in another tube we add to a similar amount of sensitized 

 blood 0.3 of a cubic centimeter of heated normal guinea-pig serum. 

 After a certain time we fill both tubes with salt solution, centrifu- 

 galize, decant the supernatant fluid,* and suspend the sedimented 

 corpuscles in 0.3 of a cubic centimeter of heated normal guinea-pig 

 serum. We then add 0.1 of a cubic centimeter of guinea-pig alexin 

 to each tube. There is no hemolysis in the tube that contained 

 antiserum, but rapid hemolysis in the other. The curing of sen- 

 sitized corpuscles, therefore, does not depend on permanent contact 

 with the antiserum. 



(D) Does the antiserum inhibit the effect of the sensitizer in 

 respect to its various manifestations? The most important prop- 

 erty of the sensitizer is to render the suitable cells susceptible 

 to destruction by alexin. But, as we have already shown, sensi- 

 tizers also have the property (a property, moreover, correlative 

 with the other) of conferring on the specific cells the power of absorb- 

 ing alexin and of so removing it from the surrounding fluid. Con- 

 sequently we must ascertain whether corpuscles that are sensitized 

 and then treated with antiserum will still fix alexin. Experimentally, 

 we find that under these conditions the alexin is not absorbed. 



Defibrinated washed ox blood is mixed with either two volumes 

 of rabbit > ox serum, 56 degrees, or of normal rabbit serum, 56 

 degrees. After sufficient contact the tubes are filled with salt solu- 

 tion, centrifugalized, and the supernatant fluids decanted. One 

 volume of salt solution is added to each blood sediment. As a 

 result we have two similar emulsions of red blood corpuscles, one of 

 which is sensitized. There are then prepared the following tubes: 

 * This washing may be repeated several times. 



