120 CHEMISTRY OF BACTERIA AND THEIR PRODUCTS 



from cultures do not seem to be any more toxic than those produced 

 by pepsin and trypsin, but violent poisons may be liberated from 

 bacteria during- autolj'sis, as Rosenow '^ has shown for the pneumo- 

 coccus and other bacteria; these poisons seem similar to or identical 

 with the so-called anaphylatoxin which is supposedly formed by the 

 difrestion of bacteria witli serum complement, and presumably they 

 are proteoses or polypeptids, but their exact nature is not known. 

 (See Anaphylatoxin, Chap, vii.) 



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 hainn 

 mechanically, but with the possible exception of the efifects of capil- 

 lary emboli (especially with anthrax), bacteria produce all their ef- 

 fects through chemical means. The poisonous chemical substances 

 produced by bacteria are commonly grouped into four classes : 



I. Products of the decomposition of the media upon which the bac- 

 teria are growing; among these the best known are the ptomdins. 



II. Soluble poisons manufactured by the bacteria, and secreted 

 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 prop- 

 erties as the true toxins; because of their intracellular situation they 

 are called endotoxins. 



IV. Poisonous protein constituents of the bacterial cell, which form 

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



■ ous effects of which are not specific and not usually responsible for 

 the disease; these are called hactcrial proteins. 



PTOMAINS 

 Ptomai'ns, 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 sub- 

 stances that bacteria caused disease, just as poisonous plants owe 

 their effects to poisonous alkaloids. It was soon found, liowever, tliat 

 the ptomains that could be isolated from cultures of pathogenic bac- 

 teria were insufficient by their.selves 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 

 changes characteristic of the diseases that the pathogenic organism 



71 .Tour. Infect. Dis., 1912 (10), 113; (11), 94. 235 and 480. 



