FOOD OF PLANTft^N GENERAL. 473 



carbonic acid in our atmosphere as^^Wind actually to exist, if some 

 regular withdrawal, a process in nature which consists essentially in the 

 fixing of carbonic acid, does not exist. A similar line of argument 

 might probably be pursued with regard to ammonia. The example, as 

 given by Liebig, fails somewhat in this, that he cannot allow that the 

 organic substances of the soil (humus) can arrive at the plants in 

 sufficient quantity to supply their need of carbon, because he proceeds 

 on the entirely false foundation, that the earth receives its water entirely 

 through the rain (which only supplies the smallest part), and only takes 

 notice of the humate of lime, and neglects the generally necessarily 

 present humate of ammonia, whereby the plant might receive more than 

 enough carbon for its consumption. On the other hand, far more easy is 

 the proof, which Liebig only hints at, that if in individual cases there has 

 been a sufficient quantity of humus to supply the plant with carbon, yet 

 there is not a sufficient amount of humus existing to cover the demand 

 made by the whole vegetable kingdom for carbon, a subject to which 

 we shall presently advert. 



I maintain that the following mode of research is the only correct one 

 to place securely and make evident the truth of the foregoing view. If 

 we disregard entirely any definite geological hypothesis, yet we must 

 admit that the earth has a history of its origin which I will attempt 

 here to sketch. Before their creation there could be no organic sub- 

 stances. Now, for the creation of these there are only two conceivable 

 conditions : either there was at once created a definite quantity of organic 

 matters, or these were formed gradually and continuously out of inor- 

 ganic substances. All the organic substance that the plant derives 

 from the organic matters of the earth, the first hypothesis, proved or un- 

 proved, supposes to occur in the following way : there is a certain quan- 

 tity of organic matter which constantly circulates between the animal and 

 vegetable kingdoms ; the products, excretions, and dead bodies of the one 

 kingdom supplying nourishment for the other. A priori, this view has 

 nothing in it improbable, but according to experience it is impossible, 

 as the processes of life in the animal, decomposition and combustion, in- 

 terfere. Through these a large part of the organic substances are con- 

 verted into inorganic combinations. The organic matters must thus 

 constantly diminish, and at length become perfectly consumed. The 

 process of combustion, it is well known, annihilates entirely organic 

 matters as such, and putrefaction and fermentation know no other 

 bounds than the perfect dissolution of organic in inorganic combinations. 

 Lastly, if we look in the process of nutrition at the collective quantity 

 of organic matters delivered in the manure for the culture of plants, we 

 shall find the following* : 



A working horse receives daily 



Of dry Organic Matters. 

 Ibs. 



Inl51bs. Hay . . .1174 

 5 Ibs. Oats . . . 4-07 

 5 Ibs. Litter . .3-40 



19-21 19-21 Ibs. 



* In this case the statements of Boussingault are used, but they should be coin- 

 pared with the results of German agriculturists in order to obtain the simplest and 

 most useful averages. 



