526 Theory of the Nutrition [Book hi. 



supplied to them from without ; and whether these elements 

 are such essential constituents of the vegetable organism, as 

 to be required for its full development.' The first question 

 appears in the present day absurd, since it implies the possi- 

 bility of elementary matter coming into being, and of certain 

 special elements coming into being in the plants themselves, 

 an idea however not unfamiliar to the nature-philosophy and 

 the vital force school. It was easy for Wiegman and Polstorff, 

 the authors of the essay that gained the prize (1842), men of 

 the new school, to answer the first question in the negative, 

 and indeed their answer to the second question involved a 

 negative answer to the first. The investigations made by 

 Wiegman and Polstorff in connection with the subject of the 

 second question were conducted in a thoroughly intelligent 

 manner, though they set out from the hypothesis that a certain 

 quantity of compounds of humic acid, as it was called, must 

 be present in the food-mixtures. Their experiments, better 

 adapted to the purpose than any previous ones, showed con- 

 vincingly that it is necessary to the normal nutrition of the 

 plant that it should take up the constituents of the ash ; the 

 observers also took into consideration a number of other 

 questions connected with nutrition, in which however we 

 may already see the influence of Liebig's book which had 

 come out during their investigations. 



This work was the one entitled ' Die organische Chemie in 

 ihrer Anwendung auf Agricultur und Physiologie,' which 

 appeared first in 1840 and was afterwards repeatedly reprinted 

 and enlarged. The name of the author, the -first chemist of 

 Germany, raised an expectation that the questions respecting 

 nutrition would be dealt with otherwise than they had hitherto 

 been, and this expectation was more than fulfilled by the 

 novelty and boldness with which Liebig cleared up the most 

 important points of the theory, seized upon all that was 

 essential and fundamental, and disregarded the unimportant 

 matter which had before only served to confuse the question. 



