USE OF GASES AGAINST HOUSEHOLD INSECTS 453 



carbon bisulfide find the effects of continued inhalation 

 of the gas to be about as follows : the unpleasant odor 

 first disappears, showing that the sense of smell becomes 

 deadened ; the heart beats more rapidly and all of the senses 

 become gradually deadened, so that the operator does not 

 realize that anything is wrong with him; before this 

 effect has proceeded far enough to be dangerous the oper- 

 ator becomes giddy and loses all sense of pain. When this 

 stage is reached, the operator should go at once into the 

 fresh air, after which all the unpleasant effects will soon 

 disappear. The danger of inhaling the vapor of carbon 

 bisulfide is very slight indeed compared with that of 

 breathing hydrocyanic acid gas. Really there is very 

 little danger in the use of this liquid because circumstances 

 under which one could inhale enough of the vapor to cause 

 death could hardly occur unless one were accidentally 

 locked in a room for some time with a quantity of the gas. 

 Its insecticidal power. The power of carbon bisul- 

 fide vapor to kill insects varies with the species of insects, 

 with the material in which the insects are living, with the 

 tightness of the box or room in which the gas is liberated, 

 with the amount of gas used, and with the period of time 

 over which the insects are exposed to the gas. For 

 instance, the grain moths are killed more easily than the 

 grain weevils. Adult insects are killed more easily than 

 the larvae and pupae in their burrows in grains of corn and 

 wheat. Adult insects when free in a room are more easily 

 killed than when burrowing in the depths of bran, flour, or 

 meal. The vapor is much more effective in a tight room 

 than in one with many openings. Finally, the vapor is 

 apt to be more efficient if its effect is continued over a 

 long period than over a short one. 



