239 



carbon and hydrogen, and four times as much oxygen, as had been 

 given to it in manure during the year, even supposing that the whole 

 amount of the nutrient qualities of the manure had entered the plants, 

 which is never the case. 



. "And thus, as the final result of our inquiry, we arrive at the fol- 

 lowing grand view of the interchange of matter between the three 

 kingdoms of Nature. Decomposition and the process of respira- 

 tion set free all vegetable and animal substances (diminishing the 

 amount of oxygen in the air) in the form of carbonic acid, ammonia 

 and water, which diffuse themselves in the atmosphere. The plant 

 takes possession of these substances, and forms from them, accompa- 

 nied by an incessant increase of the oxygen of the atmosphere, com- 

 pounds rich in carbon and hydrogen, but devoid of nitrogen, such as 

 starch, gum, sugar, and the various fatty matters, and others rich in 

 nitrogen, namely, albumen, fibrin e and caseine. These compounds 

 are for the service of the animal, which builds up its corporeal frame 

 from the latter, and burns the former in the respiratory process, for 

 the maintenance of the necessary heat. This theory stands now firm 

 and unshakable upon the facts which have been brought forward, and 

 the naturalist is perfectly correct when he says, that man, through 

 the mediation of plants in the first instance, lives upon air. Or we 

 may express it in this way : the plant collects the matters from the 

 atmosphere, and compounds from them the food of man. But life it- 

 self is but a process of combustion, of which decomposition is only 

 the final conclusion. Through this combustion all the constituents 

 return back into the air, and only a small quantity of ashes remains 

 to the earth from which they came. But from these slow invisible 

 flames rises a new Phoenix, the immortal soul, into regions where our 

 science has no longer any value." — p. 152. 



But then comes the question, " If the plant draws carbonic acid, 

 ammonia and water from the air — if this is its only source of food — 

 what is the use of manure ?" One answer to this question is derived 

 from physics, explaining the action of humus in general, the other 

 from chemistry, showing the necessity for manure, and the advantages 

 derived from its use. 



Carbonic acid, ammonia and water being the food of plants, the 

 question arises, how and by what organs do plants absorb these mat- 

 ters. Water to the amount of 99 ^ cent, at least is taken up by the 

 roots ; but plants have been proved to consume a far greater quantity 

 of water than falls in the form of rain, even supposing them to absorb 

 all the rain which falls, which is by no means the case. 



