44 INFECTION AND IMMUNITY 



or exposed to the action of hot, dry air, a much higher 

 temperature is required. This fact must constantly 

 be kept in view in carrying out practical measures of 

 disinfection, and for this reason the disinfection of 

 clothing, blankets, etc., by dry heat is rarely employed. 

 At quarantine stations and municipal disinfecting sta- 

 tions disinfection by steam is relied upon to a great 

 extent, and has been proved by experience to be su- 

 perior to all other methods. The disinfection of 

 bandages, instruments, and dressings of all kinds for 

 the " aseptic " treatment of surgical wounds is also 

 accomplished by exposure to moist heat (steam or 

 boiling water). 



In considering the value of heat as a disinfectant, 

 we must take account of the very great difference in 

 the resisting power of growing bacteria and of the 

 reproductive elements formed by some of them, 

 which are known as " spores." 



The spores of certain bacteria found in surface 

 water and in the soil may resist the temperature 

 of boiling water or of live steam for several hours, 

 but fortunately the spores of known disease germs 

 have far less resisting power. In experiments made 

 nearly twenty years ago, I found that the spores of 

 the anthrax bacillus did not grow after exposure to 

 the temperature of boiling water for four minutes. 



As already stated, bacteria which do not form 



