154 BACTERIOLOGICAL METHODS 



indicates the activities of putrefactive bacteria in culture, which 

 correspond with the putrefactive changes produced in nature: 



The rotting bacteria produce the familiar changes in meat 

 usually designated as spoiling, rotting and tainting, and such meat 

 is universally recognized as unlit for food because of the deleterious 

 effects following the ingestion of such meats. Tainted meats 

 may appear entirely normal to the naked eye and slight decay of 

 the inner tissues may not be appreciable to the sense of smell. 

 The decomposition changes resulting in the liberation of indol, 

 skatol and related substances having disagreeable odors usually 

 begin near the bones and joints, and such decomposition may not 

 become apparent until the bony structure is exposed by cutting 

 or until the odors are dissipated more actively by boiling. This 

 odor is very persistent; boiling for several hours will not cause it to 

 disappear entirely. It must not be supposed that meats free from 

 bad odors are necessarily free from ptomaines and toxins. For 

 example, perfectly fresh meat may absorb these poisonous sub- 

 stances when placed in contact with badly tainted meats and, again, 

 some toxin-forming bacteria do not produce odoriferous gases. 



The bacteriology and toxicology of canned meats and soup 

 stocks containing meat has not received the attention that it should. 

 It is these substances which are so largely responsible for the mul- 

 titudinous lesser intestinal disturbances following their use as food. 

 The present methods of canning meats should be thoroughly in- 

 vestigated and ways and means devised to improve them in 

 accord with modern advance in the manufacture of food products. 

 ,It is generally believed that the eating of canned meats and soups 

 is fraught with danger to life and health, and this is not far from 

 the truth. The proper canning of meats requires infinitely more 

 care than the canning of vegetable substances. The careful super- 

 vision of the marketing of meats and meat products is vastly more 

 important than the supervision of vegetable foods. It is compara- 

 tively rare for toxins and ptomaines to be formed in vegetable 

 substances, whereas this is the rule in the decomposition of meats. 



