172 STUDIES IN IMMUNITY. 



a, one part of normal defibrinated rabbit blood plus one part of fluid A plus 

 five parts of fresh normal guinea-pig serum. 



6, one part of normal defibrinated rabbit blood, one part of fluid B, five parts 

 of fresh normal guinea-pig serum. 



Dissolution occurs rapidly in tube a, but the corpuscles remain intact in 

 tube b. 



It is evident that red blood corpuscles fix the active substances 

 in antihematic sera with avidity. It is also found that the effect 

 of these substances on the corpuscles that leads to their agglutina- 

 tion and sensitization to alexin is very profound, since it is not 

 eliminated by several washings. These washings are easily accom- 

 plished. Several drops of salt solution containing numerous cor- 

 puscles are placed in a test tube* and a small amount of active 

 serum, heated to 55 degrees and so deprived of dissolving effect, 

 is added. The tube is filled .with salt solution, shaken and cen- 

 trifugalized ; the supernatant fluid is decanted; fresh salt solution 

 is added to the deposition of corpuscles and the washing repeated 

 several times until a deposit of well-washed corpuscles is obtained. 



These washed sensitized corpuscles are as easily dissolved by a 

 dose of fresh normal serum as are unwashed sensitized corpuscles. 



These facts seem to prove that the particular substance present 

 in the serum of vaccinated animals which resists heat and permits 

 the energetic action of the alexin acts upon the corpuscles themselves 

 in such a way as to sensitize them to the action of the alexin. We 

 might have supposed, indeed, that this particular substance acted, 

 not on the corpuscles, but directly on the alexin in a way to render 

 it more energetic. This latter hypothesis, however, is not in accord- 

 ance with facts and, moreover, would not explain so well the evident 

 specificity. It would seem to be demonstrated by the preceding 

 experiment that in a mixture of corpuscles, active heated serum, and 

 normal serum there is no reaction in the fluid part of the mixture 

 between the alexin and the particular substance of the active serum. 

 This is shown by the fact that the specific substance rapidly sepa- 

 rates from the fluid and fixes itself on the corpuscles, which then 

 become susceptible to the subsequently added alexin; this is shown 

 by adding it only after the sensitizing substance has been combined 



* In such an experiment the corpuscles employed have been previously washed 

 to remove the serum present in defibrinated blood; in such an experiment no trace 

 of alexin should be left. 



