RESPIRATION. 169 



be respired ; a tortoise lived twenty-four to thirty-six hours, 

 and frogs lived near an hour when placed in oil, while in- 

 sects died immediately, if placed in the same fluid. Fishes 

 die if the water be boiled and the air excluded ; yet gold 

 fishes have lived in water thus prepared one hour and forty 

 minutes. 



392. But if a man be^leprived of air, or of the power of 

 admitting it to the chest, the circulation of his blood will 

 generally cease within ten minutes, and his power of motion 

 within five, often within three minutes. Yet some men, by 

 long practice, acquire a power of suspending their breath for 

 this period, without suffering any apparent loss of power. 

 The divers of Ceylon are in the habit of remaining under 

 water three, four, or even five minutes, in search of pearls ; 

 and, when they come up, they seem wearfed, but not ex- 

 hausted.* 



393. This necessity of good air is imposed upon all the 

 animated creation, though in an unequal degree. Yet every 

 animal, the highest and the lowest, the man and the worm, 

 and all intermediate grades of creatures, must sustain life 

 by their breath. All of these, from the first to the last mo- 

 ment of their existence, are continually absorbing and con- 

 suming the life-giving oxygen of the air, and sending back 

 in its stead the poisonous carbonic acid gas. 



394. The air covers the whole globe, and reaches to forty- 

 five or fifty miles from it. It is so subtile, that it penetrates 

 the smallest crevice ; and, if not excluded by other matter, it 

 fills all space within forty-five or fifty miles of the earth. 

 Yet, abundant as this air is, it might be feared that the respi- 

 ration of so many millions of creatures, carried on for thou- 

 sands of years since the world began, would consume all its 

 oxygen, and leave nothing but nitrogen, and carbonic acid 

 gas, and vapor, in its place. 



395. To one who looks no farther into the order of na- 

 ture, this, perhaps, might be a reasonable fear. But a 



* Carpenter's Physiology, p. 393. 



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