136 DISINFECTION— STERILIZA TION— DISINFECTANTS 



3. Cold. — ^That cold is an excellent antiseptic is illustrated 

 by the general use of refrigerators and "cold storage." 

 Numerous experiments have shown that although many 

 pathogenic organisms of a given kind are killed by tempera- 

 tures below freezing, not all of the same kind are, and many 

 kinds are only slightly affected. Hence cold cannot be con- 

 sidered a practical means for disinfection. 



Fig. 98. — ^A "flash process" pasteurizing outfit, with holder, 

 pasteurizer; B, holder; C, cooler. 



A, flash 



4. Light. — It has been stated (p. 65) that light is destruc- 

 tive to bacteria, and the advisability of having well-lighted 

 habitations for .men and animals has been mentioned. The 

 practice of "sunning" bedclothing, hangings and other large 

 articles which can scarcely be disinfected in a more con- 

 venient way is the usual method of employing this agent. 

 Drying and the action of the oxygen of the air assist the 

 process to some extent. Undoubtedly large numbers of 

 pathogenic organisms are destroyed under natural condi- 

 tions by the combined effects of drying, direct sunlight and 



