IMMUNITY 5 



characterised by the symptoms resulting from the 

 absorption or diffusion of the poison produced by the 

 bacteria themselves. 



Bacterial Poisons. — The bacterial poisons are 

 specific products of the bacteria, dependent upon the 

 nature of the culture medium only as it favours or 

 retards to the full development of the- physiological 

 functions of the germs. The poisons produced by all 

 pathological organisms may be, to a greater or less 

 extent, of several kinds. The true toxins are soluble, 

 truly secretory products of the bacterial cell, passing 

 from them into the culture media during their life. 

 Such are the poisons of the tetanus and diphtheria 

 bacilli. There are other micro-organisms in which no 

 exotoxins are formed ; to this class belong the greater 

 number of pathogenic germs. These organisms 

 during life do not produce true toxins ; it is only after 

 death and disintegration that the poison is liberated. 

 This class of toxins is known as endotoxins. Therefore 

 we have two classes of poison produced by micro- 

 organisms : the true toxins, or extracellular poisons, 

 and the endotoxins, or intracellular poisons. 



The Mode of Action of Bacterial Poisons. — Study 

 of the toxic products of various micro-organisms has 

 shown that many of the bacterial poisons possess a 

 more or less definite selective action upon special cells 

 and tissues. Thus, certain soluble toxins of the 

 tetanus bacillus and the Bacillus hotulinus attack 

 specifically the nervous system. Again, certain 

 poisons produced by the staphylococci, the streptococci 



