VIRULENCE OF ORGANISMS 7 



composition of the media upon which the bacteria grow, and any 

 differences in constitution of ptomains are differences due to varia- 

 tions in medium rather than variations of bacteria. In this respect 

 they differ from toxins. Furthermore, it is not possible to produce 

 immune substances against ptomains. Ptomains are not to be con- 

 fused with toxins produced by bacillus botulinus, by bacillus enteri- 

 ditis, or other members of the " food-poisoning " group, which are 

 true toxins and are capable of inducing the formation of antitoxins. 

 Food poisoning may, therefore, be due to the decomposition of food 

 with the production of ptomains which are absorbed and produce 

 toxic symptoms, or may be due to the presence in food of toxins 

 produced by the bacillus botulinus and similar organisms. In addi- 

 tion to the ptomains which contain C, H and N, a fourth group 

 contains also oxygen, as exemplified in the substance sepsin ob- 

 tained from decomposing yeast cells. This is closely related to 

 cadavarin in its chemical composition and acts as a powerful dilator 

 of intestinal capillary blood-vessels from which diapedesis may occur. 



The true toxins or exotoxins are soluble and diffusible poisonous 

 substances produced by the life activity of bacteria. They may be 

 produced when the organisms exist in a parasitic state or when they 

 grow upon artificial media and the nature of a toxin for any given 

 species is not determined by the medium upon which the organisms 

 grow, except in so far as certain media favor the production of 

 greater amounts of toxin than do others. The diphtheria bacillus 

 produces the same toxin regardless of the medium upon which it is 

 grown, although nutrient veal broth is the most favorable for toxin 

 formation. The same general statement is true of the tetanus 

 bacillus and those other organisms which produce toxins. Toxins 

 are unlike ptomains in that they have not a definite chemical com- 

 position and in that they serve to induce antitoxin formation. They 

 have certain resemblances to enzymes, but are probably not identi- 

 cal with enzymes. The nature of toxins, their action, and other 

 details are considered in the chapter on toxins and antitoxins. 



The endoioxins develop within the bodies of bacteria and are not 

 secreted into the surrounding medium. They apparently are only 

 liberated upon the death and disintegration of the organisms. It is 

 not certain that they can be differentiated absolutely from the 

 poisonous bacterial proteins, and it is extremely difficult to induce 

 antitoxin formation by their use. If they are injected into an ani- 

 mal the animal may produce agglutinins and precipitins, but not 

 antitoxin. This subject also is discussed subsequently. 



Poisonous Bacterial Proteins. The whole protein of certain 

 bacteria is poisonous, and the work of Vaughan and Novy shows 

 that the split products of bacterial proteins produced by treatment 

 with alkalinized alcohol are extremely toxic. These substances 

 apparently are not specific as regards the bacteria from which they 

 originate, but owing to their poisonous properties they may add to 

 the virulence of the organisms. Similarly toxic split products may 



