52 Dr Sellei" on (he Nutrition of Plants. 



the soil a store of organic matter adequate to the develop- 

 ment of the substance of all plants and animals, as well as to 

 the repair of the annual waste in both organic kingdoms, 

 from their rise down to the period of their final extinction. 

 By the annual waste of organic substance, in both kingdoms, 

 is to be understood the amount which passes into the mineral 

 or inorganic state, without having acted as nourishment to 

 plants. 



The animal kingdom is dependent exclusively on the organic 

 matter of the vegetable kingdom for its support. Hence, it 

 follows, that, b}- the hypothesis opposed to Liebig's, both 

 organized kingdoms must be maintained at the expense of the 

 organic matter of the soil. There are only two conditions 

 under which this is possible ; either that there is no material 

 waste of organic matter in nature ; or, what is the same thing, 

 no conversion of it to any great extent into mineral substance, 

 but, on the contrary, a continual circulation of organic matter, 

 ever changing, but still preserving its organic character, from 

 the soil to the fabric of plants, and from plants to animals, 

 and so back, without actual loss of organic form, to the soil ; 

 or if there be necessarilj'^ much waste, that, after the original 

 production of the two organised kingdoms to much the same 

 extent to which they now exist, there was left in the soil a 

 quantity of organic matter adequate to supply the annual 

 waste from the beginning of the present system of things 

 downwards, and in all time to come, till the extinction of the 

 existing races of organised beings and living organisms. 



But the waste of organic matter is undeniably very great 

 over the surface of the earth. It would require a separate 

 dissertation to explain all the various modes in which organic 

 matter is unceasingly reduced to the mineral state. 



In the single function of respiration, each mammal con- 

 question, the merits of which are under consideration. The question, 

 then, as to the formation of soil must, like the origin of organic species, 

 be regarded as belonging not to the laws of nature, but to the origins of 

 things, and, therefore, forbidden in inductive science. What in this in- 

 quiry is called the beginning of the present system of things, must, con- 

 sequently, be considered as a state not essentially differing from that of 

 the earth's surface at present. 



