18 QUARTERLY JOURNAL. 



tion, it restores this same food to the atmosphere or the earth, toi 

 be again absorbed by the plant and reconverted into food, thuj 

 going an eternal round. But we will examine this subject mort 

 at large, and shall thus be enabled to perceive more distinctly th» 

 intimate and mutual relation those two great kingdoms of natun 

 sustain to each other. 



A large part of the food of plants consists of carbonic acid 

 which they absorb largely by their leaves. Though they are no 

 utterly dependent upon animals for this, yet from them they ar 

 always receiving a large supply. It has been stated already the 

 a full grown man discharges from his lungs, daily, several ounctJ 

 of carbon ; the larger animals, of course, a greater quantity. Bil 

 this is not in the form of pure carbon. The process of respiratic 

 consists in inhaling oxygen of the atmosphere into the lungs, wh( 

 it unites with the waste carbon of the body, and is exhaled as ca 

 bonic acid. Should this process be continued for a long period- ' 

 a very long one it is true would be required — and were there i ' • 

 provision for the removal of this acid from the atmosphere, ' 

 would ultimately become so abundant as to poison the whole ra ' 

 of animals. But it is absorbed by the leaves and roots of gro" 

 ing plants, to sustain their life, and thus the atmosphere is pu 

 fied. 



By the continual consumption of oxygen by the respiration 

 animals, the apprehension would be perfectly reasonable that 

 process of time this gas, so essential to their existence, would I 

 come so much diminished, as to be inadequate to their war 

 This would in fact be true, were it not for the compensating pov ' 

 of plants. The carbonic acid which they have absorbed, wh.' 

 passing through their circulation is decomposed, the carbon &^ Jll 

 in the vegetable system, and the oxygen, again liberated by 

 leaves, is restored to the atmosphere. Thus is completed one 

 in the unending chain of organic life. ' «| 



It is not the carbon exhaled alone which becomes the foodji iJis 

 the vegetable. All the solid and liquid excrements of animals 5 a 

 applied to the same use. The body itself dies, and passes to ^ Jit 

 cay. It mingles with the atmosphere and the earth, and becoiMis 

 the food of plants, to be by them converted into food for the r ^ 

 mal. And here the remarkable difference, hinted at above, ,• ^^ 

 tween the two kingdoms, becomes evident. The chi-nges in ^' '% 





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