350 Theory of the Nutrition [BOOK in. 



prosecution of this branch of science ? But these questions 

 were not raised, and the old state of things remained for the 

 time unchanged. 



As regards the scientific questions at issue between Liebig 

 and von Mohl, Schleiden, and various agricultural chemists, the 

 contest was chiefly about matters of secondary importance, and 

 among these might be included the objection that Liebig 

 knew scarcely anything of the anatomy of the plant. The 

 main point was, that he had corrected mistaken views as to 

 the way in which plants are fed, had refuted gross errors, had 

 shown what was fundamental and essential and what was 

 unimportant. Everything that was written on the subject 

 after 1840 shows that he did all this completely; the publica- 

 tions called forth by the controversy on his book occupied in 

 the main the ground which Liebig had cleared. Now every 

 body knew all at once what was meant by the decomposition 

 of carbon dioxide in the green parts of plants, that the 

 constituents of the ash are not mere seasoning to the vegetation, 

 and the like ; firm ground had been won for all, a number of 

 scientific truths had become common property for ever ; this 

 did not of course make it less meritorious in others, to test the 

 rest of Liebig's theories, or even to correct his great mistake 

 about the respiration of plants, as was done emphatically by 

 von Mohl. 



It would not be consistent with the design of this work to go 

 into all the details of the discussion excited by the appearance 

 of Liebig's book, into questions for instance respecting the first 

 products of assimilation in plants, and their further transforma- 

 tions by metabolism. Whether the primary use of the basic 

 mineral constituents is merely to fix the vegetable acids, whether 

 these acids are the first products of assimilation, or whether 

 carbo-hydrates are the immediate result of that process, 

 and similar questions, were for some time only matter of 

 conjecture, deduction and combination, unsupported by certain 

 observation obtained by suitable methods ; it was not till after 





