ANTITOXINS 



Now we come to the non-poisonous "prototoxoids" : 

 x cc + -/^ == Toxin free(ioo fatal doses.) 

 ^cc + ^ = Toxin f re e (100 fatal doses.) 

 x cc + 3^0 = Toxin free (100 fatal doses.) 

 We see here that after we have reduced the 

 antitoxin to /oo no further increase of toxicity is 

 brought about by any further reductions. Ehrlich 

 calls these toxoids " prototoxoids " because they 

 have such a high affinity for the antitoxin. But 

 there are apparently still other toxoids, as is shown 

 by the following spectrum : 



Protoxoid 



Syntoxoid 



Toxon 



100 10 200 



FIG. 4. 



Here we would obtain values as follows: 

 x ec poison + f |j{y == o, i.e. absolutely neutral. 

 x cc poison + M<T = Toxon. 

 x cc poison + Mf = Toxin free (i fatal dose). 

 x cc poison + M| --= Toxin free ( 2 fatal doses.) 

 x cc poison + M = : Toxon free (30 fatal doses.) 

 Here we find that in the middle part of the 

 " spectrum " we encounter a zone in which each %%-$ 

 antitoxin unit neutralizes one fatal dose. Ehrlich 

 believes that this part of the mixture consists of 



