NATURE OF THE ACTIVE PRINCIPLES 295 



a number of bacterial toxins Avhich lack some of the abo\e char- 

 acteristic featines, yet no justification ^vas found to exclude them 

 from the group of true bacterial toxins inasmuch as they are 

 capable of stimulating production of antitoxins after immuniza- 

 tion and are neutralized by the antitoxins according to the laws 

 goxerning the neutralization of diphtheria toxin by antitoxin. 

 There remains little doubt that in the present conception true 

 toxins may be defined as injtny-producing antigenic bacterial 

 products Avhich are capable of stimulating the production of 

 antitoxins and which are neutralized in vivo and i)i vitro ac- 

 cording to the "law of mtiltiple proportions."' The toxin-|-anti- 

 toxin reaction, therefore, is taken to be the main foiuidation for 

 definition of true toxins. As stated by W^ells, the important fea- 

 ture of the toxin-|- antitoxin reaction is that neither the toxin 

 nor the antitoxin is destroyed in the process of netitralization. 

 They appear to be iniited to each other as any other large mole- 

 ctdes may be, ^vhether chemically or by physical adsorption (Ehr- 

 lich, Arrhenius, Madsen, and J. Bordet) . I)i vitro no destruction 

 seems to take place exen when the toxin and antitoxin are to- 

 gether for long periods of time. On simple dilution of the neu- 

 tralized toxin -j-antitoxin mixtines a certain amount of dissocia- 

 tion occtirs. Such mixttues seem to dissociate gradually after 

 injection into the animal body. Incidental to neutralization of 

 toxin by antitoxin there may occur a precipitate. The precipitate 

 may be due to incidental interaction of bacterial proteins inde- 

 pendent of the toxin or may be closely related to the process of 

 neutralization of toxin xvith antitoxin. Bayne-Jones, Hazen, Eaton 

 (ig^^G/;) and others are of the opinion that in the Hocculation 

 test de\ ised by Ramon for /// vitro determination of diphtheria 

 toxin neutralization, there occins a true precipitation of diph- 

 theria toxin by its specific antitoxin. This, however, has been 

 contradicted by Bronfenbrenner and Reichert xvho considered 

 that the bacterial proteins not related to the toxin participate in 

 the reaction. 



In the cases -^vhere the precipitate formation is dtie to an inter- 

 action of bacterial proteins there may occtn- an incidental non- 

 specific inactivation of the toxin. This type of non-specific inac- 

 tivation brings about irregular neutralization, which is in 

 contrast to consistent neutralization in real toxin-(-antitoxin 

 reaction. 



During the process of aging a certain (juantity of toxin loses its 



