CHAPTER VIII. 

 TOXIN AND ANTITOXIN (continued). 



DEFINITION or TOXIN, TETANUS TOXIN, BOTULISM TOXIN, DYSENTERY TOXIN, 



STAPHYLOLYSIN. 



The diphtheria toxin and its antitoxin just discussed in detail is of 

 great practical and theoretical importance, and can serve as a type of all 

 true toxins and antitoxins. Bacterial toxins can be defined as poisons 

 given off by the bacteria, the symptoms resulting from their action appearing 

 after a certain incubation period. The invaded organism reacts by the 

 production of specific antitoxins which neutralize the toxins in amounts, 

 following the law of multiple proportions. 



Further analysis of this definition indicates that a substance can be 

 considered a toxin only when it has a poisonous action, or in the words of 

 Ehrlich when it possesses a toxophore group. 



This toxicity does not always manifest itself by necrosis or death as in 

 diphtheria. More frequently the toxin has a somewhat selective action 

 affecting a certain group of organs. Thus a toxin acting upon the central 

 nervous system or blood is designated respectively as a neurotoxin or a 

 hemotoxin. To differentiate a true toxin from other poisonous products 

 obtained from bacteria, it is important to note that all true toxins are 

 elements of secretion of the living bacteria, and can be separated from them 

 by filtration. According to this definition, poisons contained within the 

 bacterial bodies themselves, which may be liberated by various mechanical, 

 physical, or chemical means, cannot be considered as belonging to the 

 class of true toxins. These poisons are characterized by peculiar proper- 

 ties and are known as endotoxins. In addition it may be remarked that 

 inasmuch as a true toxin requires a period of incubation in order to 

 manifest its action, those toxins which act spontaneously are to be ex- 

 cluded from the former group. R. Krause nevertheless considered some 

 of the poisons isolated from the cholera and cholera-like spirilla (El Tor 

 Vibrio) as true toxins even though they lack an incubation period. 



The real essential property of a toxin is doubtlessly that one can 

 immunize against it, and be able to demonstrate the presence of antitoxins 

 within the serum of the immunized animal. Ehrlich claims furthermore 

 that the amount of antitoxin produced follows the law of multiple propor- 

 tions. By this is meant that the relationship between a definite dose of 

 toxin and the amount of antitoxin just sufficient to neutralize it, is constant ; 

 so that if ten volumes of toxin hold in bounds ten volumes of antitoxin, 



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