i>50 STATE BOARD OP AGRICUT.TURR. 



ready described appeart l. Tliat is to say, the gradual exclusion of 

 oxygen brought about general effects, in behavior and actions much resem- 

 bling those of chloroform, ether, gasoline and the other similar agents 

 mentioned in this connection. In other words, the general symptoms 

 of the dearth of oxygen resembled narcosis. The chances of recovery 

 were not equally good with all the agents given in the list. Hydro- 

 cyanic acid gas is irritating and extremely poisonous to insects. It 

 can scarcely be classed with the narcotic agents. Yet, beetles often 

 recover from it after having been deeply under its influence and ap- 

 parently dead. Chloro-naphtholium, zenolium and similar miscible oils 

 were irritating when the liquids themselves were applied, but their 

 vapors seemed truly narcotic. The one striking and perhaps significant 

 fact in all these observations was that nitrogen or hydrogen, i. e., lack 

 of oxygen, should produce effects so closely resembling the narcosis of 

 chloroform, gasioline vapor and the rest. 



(b) EFFECTS UPON RESPIRATION. 



When the general effects upon behavior and heart activity had been 

 correlated, for the fluids listed, as just described, it became interesting 

 to know what effect these same substances produced on the rate of the 

 respirator}' exchange. Furthermore, in a study of this phase of the 

 subject, it might be determined whether a plugging of a part or all of 

 the tracheal trunks of an insect by kerosene would really reduce the 

 amount of carbon dioxide given off and oxygen used. 



Other workers, studying the respiration of higher animals, had found 

 that, food and other conditions remaining as nearly as possible the 

 same, an increased excretion of carbon dioxide by an animal accom- 

 panied an increase in the oxygen used. Likewise a decrease in the 

 one meant a decrease in the other. In view of this fact, it was decided 

 to study the effects of the fluids upon the rate of carbon dioxide ex- 

 cretion only — especially since accun-ate means of determining the 

 oxygen used' by an insect did not at first suggest itself. Preliminary 

 experiments soon showed that accurate determinations of the carbon 

 dioxide excreted by treated and untreated insects could be made with 

 the help of the verv simple apparatus represented by Fig. 2. As may 

 be seen, it consisted of a flask (2260 c. c. capacity) from the rubber 

 stopper of which hung a brass wire cage for the insects. At the lower 

 end of the cage a small cap of muslin was fastened to catch any excreta 

 which might sift through the screen. Beneath the cap, could be hung 

 a small wad of absorbent material for the fluid-insecticide, in case the 

 influence of its vapor was to be tested. In the bottom of the flask 

 was placed a measured amount of standard barium hydrate solution. 

 This standard bariuim hydrate was kept in stock in a large, bottle pro- 

 tected from the air by a carbon dioxide filter. Arrangements were 

 made for drawing off and accurately measuring out the solution as it 

 was needed, by the gravity method, using a bm^ette with a two-way 

 cock. 



Before starting an experiment, the flask was connected up between 

 a carbon dioxide filter and an aspirator. Thus the air in the flask 

 could be rendered entirelv free from carbon dioxide in about 20 minutes. 

 After that, the standard barium hydrate could be quickly introduced 



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