FLIES AXD OTHER HOUSEHOLD INSECTS 49 



advisable to have one or more jars or generators in each room or 

 halhvay, since it is not wise to use more than two pounds of cyanide 

 in a generator. The large, preferably deep, earthenware vessels 

 used as generators should be placed near the middle of the room and 

 on a thick layer of newspapers in order to avoid possible injury 

 from splashing acid. Precautions should be observed, if the build- 

 ing is in contact with others in a row, to see that parties in adjacent 

 dwellings are warned and arrangements made so that the rooms 

 next the treated building will be kept well aired during the fumiga- 

 tion. It is unsafe to attempt to fumigate individual rooms in a 

 house or a building in a row, unless one can be certain that there 

 will be good aeration on all sides of the apartment or building. The 

 deadly character of this gas is shown by the destruction of sparrows 

 resting upon the eaves of a building during fumigation. One should 

 not attempt to fumigate a building or a room alone, because an ac- 

 cident under such conditions is very likely to result fatally. Since 

 hydrocyanic acid gas is lighter than air, operations should com- 

 mence at the top of the building and proceed successively from floor 

 to floor. Better still, place the requisite amount of the cyanide of 

 potassium in thin bags, suspend each over its generator in such a 

 manner that when a string near the exit is loosened, all will drop into 

 the jars. The poison should not be in a thick paper bag, as the ac- 

 tion of the acid may be seriously hindered if not almost prevented. 

 Under no conditions should any one be allowed to enter the 

 building prior to the completion of the fumigation and its thorough 

 aeration. At least 30 minutes and preferably an hour or more, 

 depending somewhat upon the means of ventilation, should be 

 allowed for this latter process. It is unsafe to enter any recently 

 fumigated building until all the odor of the gas, resembling that of 

 peach kernels, has disappeared. The contents of the fumigating 

 jars should be carefully disposed of together with any remaining 

 cyanide. These substances can either be buried deeply in the soil, 

 or if in a city, may be poured into the sewer. 



The following memoranda will doubtless prove of service in 

 practical work. 



1 Estimate the cubical contents and the amount of materials for 



each room. 



2 Remove all liquids and moist foods in particular. 



3 Seal all exits tightly with strips of paper or by filling crevices. 



4 Provide for ventilation from the outside. 



