DESTRUCTION OF BACTERIA. 



19 



is more effective than dry heat, because it has greater 

 penetration. Boiling for five minutes will destroy all 

 forms of bacteria except spores, which require boiling 

 for two hours. The destructive action is intensified 

 and the danger of rusting avoided if sodium carbonate 



Fig. 2. Arnold's steam sterilizer. 



is added to the water in amount sufficient to make a 

 i per cent, solution. Live steam is employed for steril- 

 izing dressings. The instrument most often used is 

 the Arnold sterilizer, which consists of two* metal 

 chambers, one within the other, beneath which is a pan 

 containing the water to be heated. A flame under- 

 neath boils the water and generates the steam, which 

 rises to the upper chamber and penetrates the contents. 

 The exposure of dressings in this way to live steam 



Boiling 



Steam 



