2 54 MANUAL OF BACTERIOLOGY. 



is created to carry off the gas as rapidly as formed. In opera- 

 ting, a sufficient number of tablets are placed on the tray, the 

 lamp lighted and placed in the room to be disinfected. 



Methyl-alcohol Lamps. — Several of these lamps are on the 

 market, all operating on the well-known principle of the oxida- 

 tion of wood-alcohol to formaldehyde when the alcohol is 

 vaporized by projection against a heated, platinized, asbestos 

 disk. In operating such an apparatus, the alcohol is lighted 

 until the asbestos disk becomes hot. The flame is then extin- 

 guished; the heat from the disk is sufficient to vaporize the 

 alcohol, which undergoes oxidation and keeps the disk at a 

 red heat. When the apparatus is operating in a satisfactory 

 manner, the room is closed and disinfection allowed to proceed. 

 It must be said, however, that it is difficult to estimate or 

 control the amount of formaldehyde evolved in generators of 

 this type. 



Formaldehyde Candles. — ^Mixtures of paraformalhyde and 

 paraffin or other combustibles, which may be moulded into 

 candles, each enclosed in a tin case, make a convenient ap- 

 paratus to generate formaldehyde gas for room disinfection. 

 The candle is placed in a suitable fireproof dish, it is then ig- 

 nited, and generation of the gas is allowed to proceed in the 

 tightly closed room. 



Sulphur Dioxide. — This substance is used extensively for 

 house disinfection, and is usually prepared by burning sulphur. 

 Much difference of opinion exists regarding the value of it as a 

 disinfectant. The spores of anthrax are not killed by several 

 days' exposure to the liquefied gas. Anthrax and other 

 bacilli are destroyed in thirty minutes when exposed on moist 

 threads in an atmosphere containing one volume per centum of 

 the gas. An exposure of twenty-four hours in an atmosphere 

 containing four volumes per centum of the gas will destroy the 

 organisms of typhoid fever, diphtheria, cholera and tubercu- 

 losis. The presence of moisture greatly enhances the activity 



