87 



71. It follows from the preceding series of expe- 

 riments, that the oxygenous portion of the air is 

 changed by the respiration of amphibious animals in 

 the same manner as by that of the other classes, car- 

 bonic acid, in proportion thereto, being, in all cases, 

 produced : and that when the whole, or nearly the 

 whole, of that gas is so changed, the animal no long- 

 er survives. But if the animal die when all the 

 oxygen gas is changed, and all the air that has disap- 

 peared, when the carbonic acid is removed, be oxy- 

 gen gas, then the bulk of air that remains, and is 

 unchanged, must consist wholly of nitrogen gas; 

 and, as this nitrogen gas, joined with the oxygen gas 

 that has disappeared, makes up the whole bulk of 

 air originally employed, it follows also, that, while 

 the oxygen gas of the air has diminished and suffer- 

 ed change, the nitrogenous portion has continued 

 undiminished and unaltered. 



72. During all these changes operated on the air 

 contained in water by the respiratory functions of a- 

 quatic animals, the water itself seems to suffer little 

 or no alteration. Mr Carlisle took separate glasses, 

 each containing one pound of distilled water, which 

 was previously boiled to expel all its air, and then, 

 inverting them over mercury, he put into them one 

 gold fish, one frog, two leeches, and one fresh wa- 

 ter muscle. The animals were confined several days 

 in these situations, and exposed to the sun during 

 January in temperature 43 an$l 48 Fahrenheit : but 

 no air-bubbles were produced in the vessels, nor 

 was there arty sensible diminution of the water. 

 The frog died on the third day, the fish on the 

 fifth, the leeches on the eighth, and the muscle on 



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