346 M. Dumas on the Chemical Statics of Organised Beings* 



air is consumed by animals, who convert it into water and 

 carbonic acid ; it is restored by plants, which decompose these 

 two bodies. 



But nature has arranged everything so that the store of air 

 should be such with relation to the consumption of animals, 

 that the want of the intervention of plants for the purification 

 of the air should not be felt until centuries have elapsed. 



The air which surrounds us weighs as much as 58 1,000 cubic 

 kilometres of copper; its oxygen weighs as much as 134,000 

 of these same cubes. Supposing the earth peopled with a 

 thousand millions of men, and estimating the animal population 

 at a quantity equivalent to three thousand millions of men, we 

 should find that these quantities united consume in a century 

 only a weight of oxygen equal to 15 or 16 cubic kilometres of 

 copper, whilst the air contains 134,000 of it. 



It would require 10,000 years for all these men to produce 

 a perceptible effect upon the eudiometer of Volta, even sup- 

 posing vegetable life annihilated during all this time. 



In regard to the permanence of the composition of air, we 

 may say with all confidence, that the proportion of oxygen 

 which it contains is secured for many centuries, even reckon- 

 ing for nothing the influence of vegetables, and that, neverthe- 

 less, these restore oxygen to it incessantly in quantity at least 

 equal to that it loses, and perhaps more ; for vegetables live 

 just as much at the expense of the carbonic acid furnished 

 by volcanos, as at the expense of the carbonic acid furnished 

 by animals themselves. 



It is not then for the purpose of purifying the air that these 

 breathe, that vegetables are especially necessary to animals ; 

 it is, above all, to furnish them, incessantly, with organic mat- 

 ter quite ready for assimilation j organic matter, which they 

 may burn to their advantage. " 



There is, therefore, a service necessary, without doubt, but 

 so remote, that it can scarcely be recognized, which vege- 

 tables render us, in purifying the air which we consume. There 

 is another service so immediate, that if, during a single year, 

 it were to fail us, the earth would be depopulated ; it is that 

 which these same vegetables render us by preparing our nu- 

 triment, and that of all the animal kingdom. In this, espe- 

 cially, is found the chain that binds together the two king- 

 doms. Annihilate plants, and the animals all perish of a 

 dreadful famine; organic nature itself entirely disappears with 

 them in a few seasons. 



We have, however, said, that the carbonic acid of the air 

 variestfrom 4 to 6-1 0,000th. These variations are very frequent 

 and very easy to observe. Is not this a phaenomenon re- 



