THE THEOKY OF TOXIC ACTION 195 



what holds in the case of a hemolytic serum deprived of complement by 

 heat at 55° 0. (p. 125). Kyes and Sachs further showed that in addition 

 to serum-complement a substance with definitely known constitution, 

 namely lecithin, had the property of activating the haemolytic substance 

 in cobra venom, the two apparently uniting to form an actively toxic 

 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 jnimals they stimu- 

 late the production of neutralising 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 advanced the view that the toxin molecule has a very 

 complicated structure, and contains two atom groups. One of 

 these, the haptophorous (Snrrav, 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 called the toxophorous, 

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

 is brought into relation with the cell elements, e.g., the nerve 

 cells in tetanus, by the haptophorous group. Ehrlich explained 

 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 pro- 

 portion of antitoxin molecules for its neutralisation. To the 



