HEMOLYTIC SERA AND THEIR ANTITOXINS. 203 



Antitoxin, 55 degrees; fresh alexic serum to be tested; sensitizer 

 in sufficient dose (that is, hemolytic serum heated to 55 degrees). 

 The effect of this mixture on subsequently added rabbit corpuscles 

 will indicate whether or not the alexin in the serum added is neu- 

 tralized by the antitoxin. 



A control series is made with similar mixtures containing normal 

 rabbit serum (55 degrees) in place of antitoxin. This series shows 

 the intensity of corpuscle destruction by the combined action of 

 the sensitizer and the normal sera when antitoxin is absent. 

 A third series containing normal rabbit serum, 55 degrees, plus the 

 fresh normal sera under consideration but without sensitizer is 

 also useful; this series indicates what dissolving properties are 

 present in the normal sera alone without any sensitizer. The 

 rabbit blood added to these mixtures should previously have been 

 Washed in salt solution in order to free the corpuscles from rabbit 

 serum. 



Without going into minute details of the results of such experi- 

 ments we may state that the antitoxin neutralizes guinea-pig alexin 

 efficiently, but has no effect on alexin from the rat, dog, rabbit, goat, 

 goose or hen. 



It does, however, have a distinct neutralizing effect on pigeon 

 alexin. We may therefore conclude that this anti-alexic activity 

 is relatively but not absolutely specific. With a certain exception 

 (pigeon alexin) our anti-alexin has no neutralizing effect on any 

 animal species tested except the guinea-pig. These results confirm 

 distinctly the idea that the alexin in the sera of different animal 

 species is not uniformly identical; this idea was already probable 

 from the fact that the corpuscles of a given species are attacked by 

 foreign normal sera with an intensity that varies according to the 

 species from which this serum has been obtained. 



The direct action of the antitoxin on the toxin. Our anti-alexin 

 counteracts the harmful effect of guinea-pig alexin on rabbit cor- 

 puscles. There are reasons, moreover, for believing that anti-alexin 

 combines with alexin or acts directly on this toxic substance by 

 destroying or modifying it. This conclusion, however, cannot be 

 accepted offhand, as proven. We might imagine, perhaps, although 

 it seems scarcely reasonable, that antitoxin has no effect on the 



