6'S 



or the water, a constant renewal of fresh air is re- 

 quired, while the actions of life continue. What 

 then are the changes induced on atmospheric air by 

 these several classes of animal beings, whereby it is 

 rendered so essential to the maintenance of vital ac- 

 tion ? 



53. For the first, and most accurate knowledge 

 we possess concerning the changes which the air 

 suffers by the respiration of insects, v/e are indebted 

 to the labours of the celebrated M. Vauquelin. The 

 experiments of this excellent chemist were made on 

 the grasshopper (gryllus viridissimus}, which is de- 

 scribed as having twenty-four stigmata, or breathing 

 pores, ranged parallel with, but exterior to, two 

 white lines, extending longitudinally on the middle 

 of the belly. In this insect they are of an oval form, 

 but they vary in shape in different insects : and it is 

 chiefly by their mediation, that the changes on the 

 air are effected. A female grasshopper was placed 

 in eight cubic inches of atmospheric air : it breath- 

 ed from fifty to fifty -five times in a minute, and li- 

 ved thirty-six hours. The air had not sensibly di- 

 minished in volume, but, when examined by the test 

 of lime-water, carbonic acid was detected, and after 

 this was removed, the remaining air still extinguish- 

 ed a taper. When many grasshoppers were put at 

 the same time into a given bulk of air, and left 

 till they died, the oxygen gas was nearly, but not 

 entirely, consumed : and phosphorus melted in the 

 residual air when heat was applied, but burned very 

 little. A male grasshopper lived eighteen hours in 

 six cubic inches of oxygen gas : its respiration was 

 oppressive, and it breathed from sixty to sixty-five 



