286 BACTERIA AND DISEASE 



absolutely local, producing only little reaction around them, rarely 

 passing through the body generally, and yet influencing the whole 

 body eventually by means of their ferments or toxins. Of such, the 

 best representatives are tetanus and diphtheria. The local site of 

 the bacteria is, in this case, the local factory of the disease. 



Whilst the mere bodily presence of bacteria may have mechanical 

 influence injurious to the tissues (as in the small peripheral 

 capillaries in anthrax), or may in some way act as a foreign body 

 and be a focus of inflammation (as in tubercle), the real disease- 

 producing action of pathogenic bacteria depends upon the chemical 

 poisons (toxins) formed directly or indirectly by them. Though 

 within recent years a great deal of knowledge has been acquired 

 about the formation of these bodies, their exact nature is not at 

 present known. They are allied to the proteoses, and are frequently 

 described as tox-albumens. It may be found, after all, that they 

 are not of a proteid nature. Sidney Martin has pointed out that 

 there is much that is analogous between the production of toxins 

 and the production of the final bodies of digestion. Just as ferments 

 are necessary in the intestine to bring about a change in the food 

 by which the non-soluble albumens shall be made into soluble 

 peptones, and thus become absorbed through the intestinal wall, so 

 also a ferment may be necessary to the production of toxins. Such 

 ferments have not as yet been isolated, but their existence in 

 diphtheria and tetanus is, as we have seen, extremely likely. 

 However that may be, it is now more or less established that 

 there are two kinds of toxic bodies, differing from each other in 

 their resistance to heat. It may be that the one most easily 

 destroyed by heat is a ferment and possibly an originator of the 

 other. A second division which has been suggested for toxic bodies, 

 and to which reference will be made, is intracellular and extra- 

 cellular, according to whether or not the poison exists within or 

 without the body of the bacillus. 



Lastly, we may turn to consider the action of the toxins on the 

 individual in whose body-fluids they are formed. It is hardly 

 necessary to say that any action which bacteria or toxins may have 

 will depend upon their virulence, in some measure upon their 

 number, and not a little upon the channel of infection by which 

 they have gained entrance. It could not be otherwise. If the 

 virulence is attenuated, or if the invasion very limited in numbers, 

 it stands to reason that the pathogenic effects will be correspondingly 

 small or absent. The influence of the toxins is twofold. In the 

 first place, (i.) they act locally upon the tissues at the site of their 

 formation, or at distant points by absorption. There is inflamma- 

 tion with marked cell-proliferation, and this is, more or less rapidly, 

 followed by a specific cell-poisoning. The former change may be 



