88 



the thirteenth day. This experiment was made to 

 ascertain the changes produced in water by the re- 

 spiration of aquatic animals ; but the water had not 

 undergone any chemical alteration *. 



73. From this enumeration of the principal facts, 

 concerning the changes induced on atmospheric air 

 by the respiration of all these several classes of ani- 

 mals, we obtain positive evidence, that, in most cases 

 (53. et seq.)> its nitrogenous portion, as in the 

 growth of vegetables (5. 29.), continues unaltered : 

 and since, in the remaining cases, the air in degree 

 is proved to suffer the same change, and the ultimate 

 result, viz. the display of living action, is, in all re- 

 spects, the same ; it is not, we hope, exposing our- 

 selves to the charge of too hasty generalization, or of 

 resting too much on analogy, if we conclude, that, 

 in the whole view which we have hitherto taken of 

 animal respiration, the nitrogen gas of the atmosphere 

 remains unchanged. Moreover, as this gas itself 

 suffers no change, so neither does it seem to exert 

 any influence on the animal in contact with it ; for 

 Spallanzani found, that snails could live in nitrogen 

 gas twelve hours t 5 which is as long as they live 'in 

 vacua (51.) : and, in all the experiments we have 

 made in atmospheric air, the animals did not appear 

 to die from the superabundance of nitrogen gas, but 

 from the small proportion, or total absence, of oxy- 

 gen gas. 



* Philosophical Transactions, 1805. 

 f Memoirs on Respiration, p. 3i7. 



