156 



BACTERIOLOGICAL METHODS 



FIG. 49. Typical- cultural 

 characteristics of Bacillus aero- 

 genes capsulatus (B. welchii) in 

 agar. Culture 48 hr. old. The 

 agar mass is separated by the gas 

 which is formed. (MacNeal.} 



does check the growth of all kinds of 

 bacteria and of higher fungi, but not 

 in the same ratio. For example, the 

 freezing temperature inhibits the de- 

 velopment of the usual rotting bac- 

 teria very effectually, whereas many 

 of the toxin formers multiply slowly, 

 in time forming enough of the poison 

 to produce marked symptoms of 

 poisoning when meat thus affected is 

 eaten. Little is known of the changes 

 which take place in incompletely ster- 

 ilized canned meats, and no attempt 

 has so far been made to ascertain the 

 degree of decomposition which usually 

 takes place in the meats before they 

 are placed in the cans and sterilized. 

 This is a matter of the utmost impor- 

 tance and should receive the immediate 

 attention of the food bacteriologists. 



What shall be the routine method 

 in the examination of meats? It is 

 quite evident that the methods which 

 are applicable in the examination of 

 vegetable substances are not suitable 

 in the examination of meats. We 

 hereby suggest the following outline of 

 methods applicable in the food labora- 

 tory: 



i. Direct microscopical examination of 

 meats. 



a. Bacteria on surface of meats. 



b. Mold and spores present, as in moldy 



bacon, pork, etc. 



c. Presence of bladder worms, larvae of 



parasites, etc. 



