PRESERVATION OF FOOD PRODUCTS FROM BACTERIA. 323 



spores, and the destruction of these spores by heat is difficult. 

 The remedy is, of course, quite simple. Recognizing that the 

 spoiled cans are attributable to bacterial spores which resist 

 heat, the method of preventing the trouble is the use of higher 

 temperatures or a longer exposure to the heat. Although at 

 present little is known in regard to other instances of spoiled 

 canned goods there can be no question that similar explana- 

 tions are to be made. 



So completely have these facts been known, and so thor- 

 oughly have the methods been mastered, that at the present 

 time all foods which can stand heat can be preserved by the pro- 

 cess of canning. Of course the flavors of the foods are frequently 

 changed by the heating to which they are subjected, but as a 

 rule much less than by any other method of preservation. The 

 whole problem of human food supply has been modified by 

 the development of these processes. Equally has the canning 

 industry modified agricultural problems, by enabling the farmer 

 to dispose of large quantities cf perishable products which 

 could not otherwise be handled. Canning has made possible 

 a type of intensive farming which was impossible a few years 

 ago, before the facts in regard to the relation of bacteria to 

 decay were understood, and before we knew of the success- 

 ful means at our command for destroying bacterial life. 



BACTERIA IN EGGS. 



The presence of bacteria in eggs results in trouble experi- 

 enced by every farmer, and one which it seems impossible to 

 avoid. It has been naturally supposed that eggs, when freshly 

 laid, would be free from bacteria and hence not liable to decay. 

 But this is certainly not the case. Bacteria are known to enter 

 the oviduct and contaminate the mass of the egg even before 

 its shell is deposited. Hence when the egg is laid it will fre- 

 quently contain bacteria in greater or less numbers. These 

 bacteria can obtain plenty of oxygen from the air that enters 



