302 STUDIES IN IMMUNITY 



and the goat. They find, however, that when they use goat alexin 

 the corpuscles must be more heavily sensitized (that is, more heated 

 immune serum added) than when they use guinea-pig alexin. The 

 fact, however, is not surprising. It is well known that the alexins 

 from different animals are not strictly identical; and, since they 

 differ somewhat, it would be strange indeed if they had equal hemo- 

 lytic power for a given blood cell , and it is not astonishing that the 

 corpuscles have to be made more vulnerable by a heavier sensitiza- 

 tion in order for some alexins to destroy them, whereas a weak 

 sensitization suffices with other alexins. Ehrlich and Morgenroth, 

 however, reject so simple an explanation. They think, rather, that 

 the immune serum contains two (or more) distinct sensitizers, "x" 

 and "y"; the one in greatest abundance (x) is very efficient with 

 the guinea-pig alexin, but finds no fit complement in the goat serum; 

 this first sensitizer, then, has nothing to do with an hemolysis caused 

 by goat alexin. This alexin, however, suits the second sensitizer 

 (y) of the serum very well, but, since this "y " is present in relatively 

 small amounts, a large amount of immune serum must be used when 

 goat alexin is employed. Let us accept, for the sake of argument, 

 this idea of the multiplicity of sensitizers in a given immune serum 

 in spite of its improbability, and go on to the next point. 



Ehrlich and Morgenroth have a second serum, an antiserum 

 from goats obtained by immunizing them with rabbit > ox immune 

 serum, which latter serum it neutralizes. First of all, they add to 

 a large dose of this antiserum (Dose A, let us say) a small amount 

 of rabbit > ox serum and then add ox corpuscles. These corpus- 

 cles are then washed and guinea-pig alexin added to them. There 

 is no hemolysis, showing that the sensitizing power has been abol- 

 ished by the antiserum. Their conclusion is as follows : The anti- 

 serum is antitoxic for sensitizer "x" suitable for guinea-pig alexin. 



Ehrlich and Morgenroth then perform a second similar experi- 

 ment, using in this instance goat alexin. Under these conditions 

 the antiserum apparently does not protect the corpuscles and 

 hemolysis occurs. This is the conclusion: The antisensitizer is 

 so specific that, although it can neutralize sensitizer "x," it has no 

 effect on sensitizer "y," which is particularly suited to goat alexin. 

 This fact goes to show that there are indeed two distinct sensitizers. 



Their second experiment, however, differs from the first in an 



