36 INTERNAL ANATOMY OF INSECTS. 
usual tests in both instances detected the conversion of 
the oxygen present into carbonic acid?. Precisely the 
same result was obtained by Sorg and Ellis, who, having 
placed a number of flies in nine cubic inches of atmo- 
spheric air, found them all dead by the third day, the 
oxygen entirely vanished, and a quantity of carbonic acid 
nearly equal in bulk produced®. 
It is ascertained too, that insects like other animals 
require in the process of respiration not merely oxygen, 
but such a mixture of it with nitrogen or azote as com- 
poses atmospheric air: for Vauquelin found that a grass- 
hopper placed in six cubic inches of oxygen lived only 
half as long (eighteen hours) as another placed in eight 
inches of atmospheric air; its breathing was much more 
laborious, and it died when not more than one-twentieth 
of the oxygen had been converted into carbonic acid*. 
That a large quantity of oxygen penetrates all parts of 
insects, is evident also from the acid prevalent in the 
fluids of most of them, as likewise from the wonderful 
power of their muscles. That azote is also received, 
seems probable from the ammonia which has been ex- 
tracted from the fluids of many, and from the rapid pu- 
trescence of these animals4. 
The mode, however, in which the respiration of insects 
is carried on, differs greatly from that which obtains in 
the higher animals. They have no lungs, no organs 
confined to a particular part of the body, by means of 
which the whole of the blood is regularly exposed to the 
4 Ann. de Chimie, xii. 273. 
Date L. A. Sorg, Respirat. Insect. et Verm. Ellis, Inguiry into 
Chang. prod. on Atmosph. Air by Respirat. &c. 69. 
* Ann. de Chimie, xii. 273. 4 Sprengel, Commentar. &e. 27—. 
