256 BACTERIOLOGY 



tralizing function. Of the functions of these side chains, 

 that of combination is the more permanent. 



Toxoids and Toxones. Bearing this matter of permanency 

 in mind we find that when toxins are allowed to stand, 

 acted upon by heat, light and air, for a time, they may 

 still combine, as may be determined numerically, with the 

 appropriate antidotes or antitoxins, but may show evidence 

 of diminution of their intoxicating principle. When in this 

 degenerated state they are designated as "toxoids" and 

 "toxones." 



A point of peculiar interest in connection with the true 

 bacterial toxins is the extraordinary toxicity of those with 

 which we are more or less fully acquainted. Experiment 

 leads to the belief that the toxins of diphtheria and of tetanus 

 are more highly poisonous than any other known poisons. 

 Thus, for instance, diphtheria toxin is capable of causing 

 fatal intoxication in a guinea-pig weighing 400 grams when 

 injected subcutaneously in so small a dose as 0.05 milli- 

 gram, 1 while typical tetanus is produced in a mouse by the 

 injection of 0.0001 milligram of tetanus toxin. 2 



The number of bacteria capable of elaborating true toxins 

 is very small; indeed, in so far as those of significance to 

 animal pathology is concerned, we are certain of only two 

 species having this property, viz., the bacillus of diphtheria 

 and the bacillus of tetanus. For most of the other pathogenic- 

 species their toxic action is referable, not to toxins, as defined 

 above, but rather to toxic components of the bacterial cells, 

 the endotoxins or intracellular toxins. 



The Endotoxins or Intracellular Toxins. The term Endo- 

 toxin is generically used to designate a toxic, protein com- 

 ponent of the bacterial cells, i. e., it is part and parcel of the 



1 Roux and Yersin, Annals de 1'Inst. Pasteur, 1889, iii, p. 287. 



2 Brieger and Cohn, Zeit. f. Hyg. u. Infekt., 1893, Bd. xv, Heft 1. 



