TOXIC BACTERIAL PRODUCTS 43 



containing isatin dissolved in concentrated sulphuric acid. The 

 red colour of the isatin solution is changed to olive or grass-green 

 by the mercaptan. 



Toxic bacterial products. Many of the metabolic pro- 

 ducts of bacterial activity are toxic, and the disease com- 

 plex induced by an infection is for the most part caused 

 by these toxic substances, which may be classified as 

 follows : 



(1) Decomposition products. These are substances pro- 

 duced by the decomposition of the medium upon which 

 the bacteria are growing. Thus proteoses are formed by 

 the anthrax bacillus and by the pyogenic cocci. 



The ptomines form another group of these substances. 

 They are nitrogenous bodies mostly solid and crystalline, 

 related chemically to the vegetable alkaloids, and formed 

 by the action of bacteria on protein and albuminoid 

 matter. They occur naturally in decomposing and 

 putrefying food, meat, fish, etc., and as many of them are 

 virulent poisons they are of considerable practical import. 

 Poisoning by tainted food, particularly tinned meats and 

 fish, may be due to the absorption of such toxic ptomines, 

 and this form of food-poisoning is known as ptomine 

 poisoning. A number of toxic ptomines were isolated by 

 Brieger from cultivations of pathogenic microbes, and 

 at one time they were regarded as the specific poisons of 

 such organisms. 



Brieger 's work, however, needs revision, for it is 

 likely that some of the ptomines isolated by him were 

 artifacts and not actually formed by the organisms. 



Stevenson obtained traces of a highly poisonous crys- 

 talline ptomine from some sardines that had caused death. 

 Vaughan isolated a body, tyrotoxicon, apparently identi- 

 cal with diazobenzene, from poisonous cheese and milk. 

 It seems to be developed by the action of organisms 

 belonging to the B. coli or B. lactis aerogenes types. Mytilo- 



