ANTITOXINS 



37 



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 



1 100 ' 

 FIG. 4. 



Toxon 



160 



200 



x cc poison + 

 x c poison + 

 x cc poison + 

 x cc poison 4- 

 find 



Here we would obtain values as follows: 

 of* poison + f %% = o, i.e. absolutely neutral. 



= Toxon. 



= Toxin free (i fatal dose). 



= Toxin free ( 2 fatal doses.) 



= Toxon free (30 fatal doses.) 

 that in the middle part of the 



Here we 



" spectrum " we encounter a zone in which each 3 

 antitoxin unit neutralizes one fatal dose. Ehrlich 

 believes that this part of the mixture consists of 

 equal parts of syntoxoid and toxin that is to 

 say, he believes there are also toxoids which 

 have the same degree of affinity for antitoxin 

 that this toxin has. He speaks of these as " syn- 

 toxoids." 



By following out this conception of the toxin- 

 antitoxin combination, Ehrlich comes to the con- 



