AGGLUTINATION AND DISSOLUTION. 173 



with the corpuscles. Similar experiments may be made with bac- 

 teria and their corresponding antisera.* We may consider, then, the 

 conception that we previously arrived at, namely, that specific sera 

 contain a sensitizing substance that renders the corpuscles or bacteria 

 susceptible to attack on the part of the alexin, as sufficiently proved. 



We have not yet considered the close analogies between the 

 properties in the serum of a guinea-pig active against rabbit blood 

 and those present in the serum of a rabbit active against hen blood. 

 There is, however, a difference between these two sera that should 

 be noted. 



As we have already noted in a previous article, active guinea-pig 

 serum heated to 55 degrees when added to defibrinated rabbit blood 

 still produces a slight effect on these corpuscles, as is shown by a 

 distinct reddish coloration of the fluid. This is due, as we have 

 already noted, to the fact that these corpuscles are slightly attacked 

 by the small amount of rabbit alexin present in the defibrinated 

 blood. If, indeed, corpuscles previously washed in salt solution are 

 used instead of ordinary defibrinated blood, no dissolution takes 

 place; that is to say, the alexin has been eliminated by washing. 

 On the other hand, if to such washed corpuscles, subsequently sen- 

 sitized, a sufficient dose of normal rabbit serum is added, complete 

 and rapid dissolution occurs. Rabbit corpuscles, then, under the 

 influence of the sensitizing substance, become susceptible to the 

 action of their proper alexin. We should expect that hen cor- 

 puscles when treated with active heated serum (from a rabbit 

 injected with hen blood) would dissolve in normal hen serum. Such 

 dissolution, however, does not- occur. In spite of the effect of the 

 sensitizing substance hen corpuscles do not become susceptible to 

 hen alexin. 



This shows clearly enough that the alexins are not quite identical 

 in different animal species. Their more important characteristics" 

 are common ; that is, they act more or less in the same way on a 

 given bacterium, but they show differences in their action upon 

 red blood cells. The idea, moreover, was a priori evident from a 

 study of the effect of normal sera on corpuscles, from which we 



* Cholera vibrios treated with cholera serum and then carefully washed show 

 granular transformation upon the addition of normal serum or when introduced 

 in the peritoneal cavity of a normal guinea-pig. 



