28 IMMUNE SERA 



x cc poison 4- M<! = Toxin free (i fatal dose). 



oc cc poison + Mf = Toxin free ( 2 fatal doses.) 



x cc poison 4- ^B = Toxon free (30 fatal doses.) 



Here we find that in the middle part of the 

 " spectrum " we encounter a zone in which each ^"o 

 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- 

 clusion that diphtheria poison is a very complex 

 substance, containing toxin, toxon, and perhaps still 

 other primary secretion products in addition to the 

 various secondary modifications of these, toxoids, 

 toxonoids, etc. It is difficult to escape the feeling 

 that the existence of some of these hypothetical 

 substances is more apparent than real. 



Views of Arrhenius, Bar del and Others. Bordet 

 and others refuse to accept Ehrlich 's views and 

 the whole matter is still unsettled. Thus the exist- 

 ence or non-existence of toxons has excited a great 

 deal of discussion among investigators. 



The great Swedish chemist, Arrhenius, has given 

 much attention to the toxins; and has applied 

 the principles of physical chemistry to the toxin- 



