POISONOUS BACTERIAL PRODUCTS 115 



tion of tissue and exudates in suppuration, but as compared 

 with the leucocytic enzymes their influence is probably minute ; 

 beyond this they have no apparent influence upon their host, 

 and are chiefly concerned in the metabolism of the bacteria. 

 The proteoses and peptones produced by bacterial action do not 

 seem to be any more toxic than those produced by pepsin and 

 trypsin. 



POISONOUS BACTERIAL PRODUCTS 



Almost without exception all the harm that bacteria do is 

 brought about by means of the chemical substances produced in 

 one way or another by their metabolic processes. Animal 

 parasites may do harm mechanically, but with the possible 

 exception of the effects of capillary emboli (especially with 

 anthrax), bacteria produce all their effects through chemical 

 means. The poisonous chemical substances produced by bac- 

 teria may be grouped into four classes : 



I. Products of the decomposition of the media upon which 

 the bacteria are growing ; among these the best known are the 

 ptomains. 



II. Soluble poisons manufactured by the bacteria, and se- 

 creted from the cell into its surrounding media the true toxins. 



III. Poisons manufactured by the bacteria which do not 

 escape from the normal cell, but which are as specific in their 

 poisonous properties as the true toxins ; because of their intra- 

 cellular situation they are called endotoxins. 



IV. Poisonous proteid constituents of the bacterial cell, which 

 form part of the cell protoplasm, but which are not soluble and 

 the poisonous effects of which are not specific and not usually 

 responsible for the disease ; these are called bacterial proteids. 



PTOMAINS 



Ptomains, the soluble basic nitrogenous substances that are 

 found in the medium in which bacteria have been growing, were 

 the first bacterial products that were recognized, and for some 

 time it was believed that it was through the production of such 

 alkaloid -like substances that bacteria caused disease, just as 

 poisonous plants owe their effects to poisonous alkaloids. It 

 was soon found, however, that the ptomains that could be iso- 

 lated from cultures of pathogenic bacteria were insufficient by 

 themselves to cause the poisonous effects that such cultures 

 produced when injected into animals. The isolated ptomains 

 were not only far less poisonous than the original culture, but 

 furthermore they did not produce the symptoms and anatomical 



