192 THE TOXINS PRODUCED BY BACTERIA 



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 neuro-toxin excreted by the 

 diphtheria 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 distinct 

 from neurotoxin production, and therefore requiring another 

 mechanism for its neutralisation. The complexity of the toxic 

 process is also illustrated by the facts known regarding the 

 cholera vibrio. In man, this organism is confined in its habitat 

 to the intestinal tract, and its serious effects are attributed to 

 the absorption of toxins therefrom. On the other hand, in 

 animals, not susceptible to such intestinal infection, death can 

 be readily produced by the injection intraperitoneally of a com- 

 paratively small amount of dead cholera vibrios, and it will be 

 seen in the chapter on Cholera that the possibility has to be 

 faced of the toxins acting in the two conditions being different. 

 Thus it is possible that the toxic element in an organism which 

 enables it to effect its initial multiplication in or on the tissues 

 is not necessarily bound up with the toxicity which is respons- 

 ible for the manifestation of specific disease effects. This is 

 borne out by the work of Grassberger and Schattenfroh on the 

 bacillus of symptomatic anthrax. In this case an organism, 

 which in vitro has lost to a large extent its capacity of producing 

 soluble toxins, may show great capacity for multiplying when 

 introduced into a susceptible animal. 



There is another point which must be kept in view, namely, 

 that some of the phenomena which have been regarded as 

 dependent upon the activity of bacterial toxins may possibly 

 be related to the little-understood process of anaphylaxis (see 

 Immunity). Anaphylaxis essentially consists in the develop- 

 ment under certain circumstances in an animal of a hypersensi- 

 tiveness to foreign albuminous materials which in themselves 

 are not essentially toxic. Effects of the gravest kind may be 

 produced during this period of hypersensitiveness, and it has 

 been thought that some of the phenomena of an infectious 

 disease, e.g. the occurrence of an incubation period, may be 



