Dr Seller on the Nutrition of Plants. 53 



Slimes annually much more than its own weight of carbon, 

 which is but one of the constituents of organic matter. 

 Birds consume more, the less perfect animals consume less. 

 Hence it cannot be an over-estimate to assume, that, on an 

 average, every living creature annually destroys in respira- 

 tion alone, its own weight of the carbon of organic com- 

 pounds. In insects, the consumption of oxygen, which is a 

 near measure of the carbonic acid thrown out in respiration, 

 is as great compared with their weight as in mammals ; and 

 the quantity destroyed by mammals, in proportion to their 

 weight, is nearly the mean between the greater amount con- 

 sumed by birds, and the less amount required for the respira- 

 tion of cold-blooded animals in general. The objection of 

 Berzelius, that the carbon consumed in respiration is over- 

 rated, because it is more than equal to the whole carbon in 

 the average amount of food, plainly involves an over-estimate 

 of the average proportion of water, and an under-estimate of 

 the average proportion of carbon, in the diet of men ; he makes 

 the water three-fourths of the weight, and the carbon one-half 

 of the remainder, which is true of only a few articles of food. 

 A second great source of the conversion of organic matter 

 into carbonic acid is the burning of Avood in fires, of lamp-oil, 

 of tallow and wax in candles, of cotton and rushes for wicks, 

 and of other such vegetable and animal substances in domestic 

 life. Thus the means of keeping himself warm, of cooking his 

 victuals, and of supplying himself with light in the absence of 

 the sun, — conveniences not voluntarily dispensed with by any 

 individual of the millions of the human race — involve a daily 

 consumption of much organic matter all over the globe, ex- 

 cept in the few localities in which a supply of heat and light, 

 in the shape of coal, is afforded from the organic remains of 

 a former world. Of the quantity of wood destroyed in com- 

 mon lires, one may judge from the fact, that Great Britain, 

 containing less than a fiftieth part of mankind, at a moderate 

 calculation, consumes annually, besides peat and wood, 

 20,000,000 of tons of coal, 17,000,000 of which are reckoned 

 to be for mere domestic use. Accidental conflagrations, and 

 the too frequent ravages of war, in houses, ships, forests, 

 and the like, swell the amount of waste by fire. A candle 



