IMMUNITY AND SUSCEPTIBILITY. 133 



theory of Behring, Ehrlich, Kanthack, and their fol- 

 lowers, who, mixing toxin and antitoxin in vitro and in- 

 jecting it into the body, see in the inertness of the 

 mixture a chemic neutralization of the toxin, which is 

 destroyed in the process. 



A few experiments made in the same line as those of 

 Behring and Ehrlich seem very convincing. Thus if x 

 toxin is mixed withjy antitoxin, x+y becomes an inert 

 mixture. 10 x + 10 y and 100 x + 100 y are similarly 

 inert. Of course, supposing that one of the other 

 theories is correct, there is no real reason why definite 

 proportions should not work out in the same way. 

 There can be no doubt that the addition of antitoxin 

 to toxin alters it chemically to a certain degree. Thus the 

 experiments of Ehrlich with ricin are very instructive. 

 If ricin is added to blood, the coagulation of which is 

 prevented by citrate of sodium, the corpuscles agglu- 

 tinate in masses and sediment. If, however, some anti- 

 ricin — the serum of an animal immunized to ricin — be 

 added to the blood before the ricin, the agglutination of 

 the corpuscles does not take place. The reaction is a 

 definite quantitative one. 



The action of antiricin upon ricin is viewed by Ehrlich 

 as one akin to the formation of the double salts, one 

 molecule of the antitoxin combining with a definite un- 

 changeable quantity of toxin, the process being hastened 

 by heat and retarded by cold and dilution. 



Kossel has shown, that the blood of the poisonous eel 

 dissolves the blood corpuscles of animals into which it is 

 injected. When eel serum is added to defibrinated blood 

 from animals for which it is poisonous, the coloring 

 matter is quickly dissolved from the corpuscles. If, 

 however, some serum from an immunized rabbit is added 

 to the blood beforehand, the eel's serum fails to dissolve 

 out the hemoglobin. In this experiment the quantity 

 of the serum of the animal immunized to the eel's blood 

 must be directly proportional to the quantity of eel's 

 blood used. 



