FERMENTS, ENZYMES, TOXINS AND PTOMAINS 49 



aerobic bacteria do not have this function, or bring about 

 the alteration so slowly that it is concealed by the simul- 

 taneous production of alkali. Among the acids formed by 

 bacteria, besides carbon dioxide, we have lactic, acetic, 

 butyric, propionic, and formic; and frequently there is 

 also produced ethyl alcohol, aldehyde, and acetone. 



The lactic acid formed by the action of different bacteria 

 on carbohydrates may be either dextrorotatory or levoro- 

 tatory, or almost equal quantities of both forms may be 

 present and the mixture be optically inactive. 



Bacterial Proteins. The proteid matter making up the 

 bodies of many species of bacteria, even those not conspicu- 

 ously pathogenic, was shown by H. Buchner to induce dis- 

 ease when isolated and injected into the tissues of animals ; 

 in some cases causing only slight fever, in others acute 

 inflammation with suppuration. For such compounds he 

 suggested the name "bacterial proteins." 



Ptomains. Ptomains, or as they are sometimes called 

 "putrefactive alkaloids" or "cadaveric alkaloids," are 

 crystallizable, nitrogenous bodies that are the results of 

 bacterial action upon dead organic matter. They differ 

 from enzymes in that they are the occasional results of 

 defective bacterial metabolism and from both toxins and 

 enzymes in that they are crystallizable and of definite 

 chemical composition. Some of them are poisonous, many 

 are not. The conditions favorable to the elaboration of 

 ptomains by bacteria vary, but in the main the most 

 poisonous of the ptomains appear to be the result of bac- 

 terial activity under a limited supply of oxygen. Poisonous 

 ptomains are sometimes formed within the intestinal canal 

 of man either as a result of malfermentation or of interruption 

 of normal oxidation. We have no reason for believing that 

 4 



