2i8 INFECTIOUS AND PARASITIC DISEASES. 



although only occurring in a vegetative form, can with- 

 stand the temperature of boiling water (212° F., 100° C.) 

 for ten minutes. In practical work, boiling, where 

 possible, is resorted to for all vegetative forms of bacteria, 

 the length of time depending upon the mass of material 

 to be disinfected. 



Spores of bacteria are quite difficult to kill. Where 

 the apparatus is at hand, steam under a pressure of 

 from twenty to twenty-five pounds (temperature 230° F., 

 105° C. — 240° F., 115.5° C.) is used. If steam under 

 pressure is not available, boiling for an hour in a closed 



Fig. 26. — The Pot Method of Burning Sulphur. (Rosenau.) 



vessel is a safe rule. Fortunately, none of the epidemic 

 diseases is caused by a spore-forming microbe, a fact 

 which lightens greatly the burden and responsibility 

 imposed upon the disinfector. 



Two gaseous disinfectants are in common 

 Gaseous ^^^ throughout the world, formaldehyde 

 and sulphur dioxide. Of these, formal- 

 dehyde approaches more nearly our concep- 

 tion of an ideal disinfectant than does sulphur dioxide 



