354 RAMBLES OF A NATURALIST. 



attacking the Termites. I relied upon the aid which 

 I might derive from some of those gaseous poisons 

 prepared by chemistry, and which in consequence of 

 their very nature are able to penetrate into the 

 smallest recesses. I had heard one of the founders 

 of modern science relate the manner in which he 

 had exterminated the Rats which continued to infest 

 his house, notwithstanding the snares and traps of 

 every kind which had been employed for their de- 

 struction. After having carefully closed all the 

 holes made by these rodents, M. Thenard applied to 

 one of the openings an apparatus from which sul- 

 phuretted hydrogen was disengaged, and the Rats 

 being thus imprisoned and compelled to breathe only 

 a vitiated air, were soon killed by the poison. 



In consequence of the special mode of respiration 

 of insects, the Termites must be much more sensitive 

 than Rats to the action of a deleterious gas.* In 

 order to render the process of gaseous injection ap- 

 plicable to them, two conditions would be necessary. 

 It would be requisite that their edifices should pre- 

 sent a continuous line of galleries and compartments 

 through which the gas might universally penetrate, 

 and this was a point satisfactorily settled by my 

 observations. Next it would be necessary to find a 

 gas which would be as destructive to those insects 



* It is well known that in insects respiration is not accomplished 

 by lungs, that is to say, by a localised organ, but by tracheae or 

 ramified canals, which convey the air into all parts of the body. 

 It will readily be understood that in these animals, a gaseous poison, 

 which is conveyed simultaneously to every portion of the organism, 

 must, all other things being equal, act with the greatest energy. 



