August 23, 1901.] 



SCIENCE. 



287 



indications of life. The dose had been suffi- 

 ciently strong, but had not been allowed to 

 remain long enough to kill the more re- 

 sistant of the roaches. 



The third and most satisfactory experi- 

 ment of the series was conducted on the 

 evening of June 20, 1901, when an applica- 

 tion of .10 gram per cubic foot was allowed 

 to remain in the building over night. On 

 the following morning the gas had not en- 

 tirely escaped, and house-flies, centipedes, 

 spiders, cockroaches, and mice were dead, 

 with the exception of a few roaches that 

 had secreted themselves between the sash 

 and frame of a loosely fitting window and 

 had thus secured enough pure air to pre- 

 vent their being killed. 



To convey an idea of the injury caused 

 by the presence of large numbers of roaches 

 in this laboratory it might be stated that 

 frequently preceding this last fumigation, 

 photographic plates placed on racks to dry 

 and allowed to remain on a table for one 

 hour were completely ruined by having the 

 films eaten from the glass ; packets of seeds 

 stored in mouseproof tin boxes were so eaten 

 as to allow the seeds to escape and in many 

 cases the seeds themselves were destroyed. 

 Since this fumigation no inconvenience has 

 been caused by the work of roaches or mice. 



By aid of the results obtained from the 

 above experiments, together with our pres- 

 ent knowledge of the action of hydrocyanic 

 acid gas in exterminating greenhouse and 

 scale insects, it may be stated that a dwell- 

 ing, office, warehouse or any building may 

 be economically cleared of all pests, pro- 

 vided that the local conditions will permit 

 the use of this gas. It probably would be 

 dangerous to fumigate a building where 

 groceries, dried fruits, meats, or prepared 

 food materials of any kind are stored. Air 

 containing more than 25 per cent, of the 

 gas is inflammable, therefore it would be 

 well to put out all fire in an inclosure be- 

 fore fumigating. Hydrocyanic acid in all 



its forms is one of the most violent poisons 

 known and no neglect should attend its use. 

 There is probably no sure remedy for its 

 effects after it has once entered the blood of 

 any of the higher animals. When cyanide 

 of potassium is being used it should never 

 be allowed to come in contact with the skin 

 and even a slight odor of the gas should be 

 avoided. Should the operator have any cut 

 or break in the skin of the hands or face it 

 should be carefully covered with court 

 plaster to prevent the gas coming in con- 

 tact with the flesh, or the possibility of a 

 small particle of the solid compound get- 

 ting into the cut, which would cause death 

 by poisoning within a few minutes' time. 



Hydrocyanic acid gas should not be used 

 in closely built apartments with single walls 

 between, as more or less of the gas will 

 penetrate a brick wall. An inexperienced 

 person should never use cyanide of po- 

 tassium for any purpose, and if it be 

 found practicable to treat buildings in gen- 

 eral for the extermination of insects the 

 work should be done only under the di- 

 rection of competent officials. Our experi- 

 ments have shown that a smaller dose and 

 a shorter period of exposure are required to 

 kill mice than for roaches and household 

 insects generally, and it readily follows 

 that the larger animals and human beings 

 would be more quickly overcome than 

 mice, since a smaller supply of pure air 

 would be required to sustain life in mice, 

 and small openings are more numerous than 

 large ones. 



The materials employed and the method 

 of procedure are as follows : After ascer- 

 taining the cubic content of the inclosure, 

 provide a glass or stoneware (not metal) 

 vessel of two to four gallons capacity for 

 each 5,000 cubic feet of space to be fumi- 

 gated. Distribute the jars according to 

 the space and run a smooth cord from each 

 jar to a common point near an outside 

 door where they may all be fastened ; sup- 



