198 THE TOXINS PRODUCED BY BACTERIA 



substance. So far no example of the activation of a bacterial toxin is 

 known, but the results mentioned point to the possibility of this occurring 

 in some cases in the tissues of the body. 



There is another group of toxic manifestations which present some 

 analogies to those of the bacterial toxins, but concerning which very little 

 is known. The best example of these is found in the toxic properties of 

 the serum of the eel. If a small quantity of such serum, say '25 of a c.c., 

 be injected into a rabbit subcutaneously, death occurs in a few minutes. 

 Although nothing is known of the substances giving rise to such effects, 

 the phenomenon is to be considered in relation, on the one hand, to 

 the action of bacterial toxins, and on the other to the phenomenon of 

 anaphylaxis. (See Chapter on Immunity.) 



The Theory of Toxic Action. While we know little of the 

 chemical nature of any toxins, we may, from our knowledge of 

 their properties, group together the tetanus and diphtheria 

 poisons, ricin, abrin, snake poisons, and scorpion poisons. 

 Besides the points of agreement already noted, all possess the 

 further property that, as will 'be afterwards described, when 

 introduced into the bodies of susceptible animals they stimu- 

 late the production of substances called antitoxins. The 

 nature of the antagonism between toxin and antitoxin will 

 be discussed later. Here, to explain what follows, it may be 

 stated (1) that the molecule of toxin forms directly a combina- 

 tion with the molecule of antitoxin, and (2) that it has been 

 shown that toxin molecules may lose much of their toxic power 

 and still be capable of uniting with exactly the same proportion 

 of antitoxin molecules. From these and other circumstances 

 Ehrlich has advanced the view that the toxin molecule has .a 

 very complicated structure, and contains two atom groups. One 

 of these, the haptophorous (aTrreu/, to bind to), is that by 

 which combination takes place with the antitoxin molecule, and 

 also with presumably corresponding molecules naturally existing 

 in the tissues. . The other atom group he calls the toxophorous, 

 and it is to this that the toxic effects are due. This atom group 

 is bound to the cell elements, e.y. the nerve cells in tetanus, by 

 the haptophorous group. Ehrlich explains the loss of toxicity 

 which with time occurs in, say, diphtheria toxin, on the theory 

 that the toxophorous group undergoes disintegration. And if we 

 suppose that the haptophorous group remains unaffected we can 

 then understand how a toxin may have its toxicity diminished 

 and still require the same proportion of antitoxin molecules for 

 its neutralisation. To the bodies whose toxophorous atom 

 groups have become degenerated, Ehrlich gives the name toxoids. 

 The theory may afford an explanation of what has been sus- 

 pected, namely, that in some instances toxins derived from 



