PREVENTIVE MEDICINE 215 



to people who do not understand the basic principles of cleansing 

 and disinfection. 



AERIAL DISINFECTION. 



FUMIGATION. Gaseous disinfection was at one time carried out 

 to a very great extent, and much dependance was placed on the 

 supposed power of the generated gases to destroy pathogenic organ- 

 isms. It is now known that the utility of gaseous disinfection is 

 very limited, and that the " disinfection," even under the most 

 favourable circumstances, is mostly unsatisfactory. It may, how- 

 ever, sometimes be used as an adjunct to other measures with 

 profit. 



Fumigation has for its object the disinfection of the air in a 

 room or building, and the penetration of the gas into every part. 

 To be effective, the room or building must be rendered air-tight, 

 otherwise constant dilution of the gases occurs. Even with 

 the room of an ordinary dwelling-house it is extremely difficult to 

 prevent this dilution. In stables and byres, &c., it is a physical 

 impossibility. The only circumstance under which in veterinary 

 practice it might be used are in suitably-constructed loose-boxes, 

 and in dog kennels and catteries. 



Fumigation of ships is also of benefit, but chiefly for the lethal 

 effect of the gas on vermin which might be disease carriers. 



Three gaseous disinfectants are used sulphurous acid gas, 

 chlorine gas, and formic aldehyde. 



SULPHUROUS ACID GAS. Sulphur Dioxide. This is generated 

 by burning flowers of sulphur or sulphur in the stick form in a room, 

 the atmosphere of which is moist. In order to be effective 3 pounds 

 of sulphur should be burned for each 1000 cubic feet of space. It 

 is of the greatest importance that the atmosphere be moist, the com- 

 bustion of sulphur in a dry atmosphere is useless so far as any 

 germicidal action is concerned. The SO 2 produced by the com- 

 bustion of the sulphur unites with the oxygen in the building to 

 form SO 3 , and this combines with the moisture in the air to form 

 H 2 SO 4 . Hence the necessity of the air being made moist before 

 combustion is started. In loose-boxes, stables, &c., this is easily 

 done by washing down the stalls, walls, &c., with the hose pipe. 

 Three pounds of sulphur per 1000 cubic feet will yield 3 per cent, 

 of the gas in the building. 



The sulphur should be placed in a tin, and if sticks are used they 

 should be broken in pieces to facilitate combustion, a little alcohol 

 added, and then ignited. Specially prepared candles are more 



