FACTS REGARDING BACTERIAL TOXINS 197 



a few processes, for example, diphtheria and tetanus, in which 

 very characteristic effects are produced on special tissues, these 

 being accounted for by the formation of soluble toxins which 

 are capable of being separated from the bacterial growths in vitro. 

 On the other hand, we have the great mass of bacterial infec- 

 tions. With regard to these, the distribution of the bacteria 

 in the bodies of infected animals makes it necessary for us 

 to take for granted that a toxic action is at work. All that 

 we know, however, regarding a possible explanation of such 

 toxicity is that the bodies of the bacteria or substances directly 

 derived from them are capable of producing pathogenic effects. 

 These effects are of a non-specific character in the sense that 

 they are not the result of an action on any particular tissue in 

 the body, but on the vital processes of the organism as a whole. 

 We are at present entirely ignorant of the interpretation to be 

 put, for instance, on the lowering of bodily temperature on the 

 one hand and of the occurrence of fever on the other, both of 

 which may be produced by the injection of the so-called intra- 

 cellular toxins in varying doses, and we are ignorant of the 

 relations which either event may have to the bringing into play 

 of the defensive mechanisms of the body. At the same time we 

 must admit the possibility that with any one species of organism 

 different effects may be produced by, it may be, different elements 

 in the protoplasm of the invading bacterial cell. Some of these 

 elements may act on certain groups of specialised cells of the 

 body, such as those of the nervous system, liver, or kidneys, 

 giving rise to what we are forced to describe in general terms 

 as disturbances of metabolism. Other poisonous elements may 

 mainly act on the defensive cells of the body, of which the 

 leucocytes may be taken as the type. Here a small dose of 

 toxin may stimulate these cells to an activity which results in 

 the infection being thrown off, either by the poison being neutra- 

 lised, or by the supply of toxin being cut off by the killing of 

 the bacterium producing it. A large dose of such a toxin, may, 

 on the other hand, altogether break down the defensive mechanism 

 of the invaded body. A possible complexity in toxic action 

 may occur even in such an apparently simple case as diphtheria. 

 As will be seen later, the special toxin excreted by the diph- 

 theria bacillus can be neutralised by an antitoxic substance, 

 but the action of this does not necessarily cause the death of 

 the bacteria in the throat whose capacity for multiplication 

 may be dependent on a vital activity of the protoplasm dis- 

 tinct from toxin production, and therefore requiring another 

 mechanism for its neutralisation. The complexity of the toxic 



