454 Theory of the Nutrition [BOOK m. 



while the larger part of their physiological axioms were not 

 derived from observations on plants at all, but from philosophi- 

 cal principles, and especially from analogies taken from the 

 animal world. 



The first step towards a scientific treatment of the doctrine 

 of nutrition was an enlargement and critical examination of the 

 materials to be gained from experience ; nor were any difficult 

 observations or experiments needed to discover contradictions 

 between the truths of nature and the old philosophy ; all that 

 was necessary was to look into things more closely and to judge 

 of them with less prejudice. 



In this way Jung was led to oppose one important point 

 of the Aristotelian account of nutrition. In the second frag- 

 ment of his work ' De plantis doxoscopiae physicae minores ' 

 is to be found a remark, which is evidently directed against 

 the notion that plants receive their food already elaborated 

 from the earth, and therefore give off no excrements 1 . Plants, 

 says Jung in accord with Aristotle, appear not to need a 

 thinking soul (anima intelligente), which would be able to 

 distinguish wholesome from unwholesome food, and Aristotle 

 therefore provided them with food which had already been 

 perfectly prepared in the earth. But Jung takes another 

 view founded on actual observation. It is very possible, he 

 says, that the openings in the roots which take in liquid matter 

 are so organised, that they do not allow every kind of juice to 

 enter, and who can say that plants have the peculiarity of only 

 absorbing what is useful to them, for like all other living crea- 

 tures they have their excreta, which are exhaled through the 

 leaves, flowers, and fruits. But among these he reckons the 

 resins and other exuding liquids, and says that it is possible 

 after all that a large part of the juices of plants escapes by 

 imperceptible evaporation, as happens in animals. 



1 See the Fragments of Aristotelian phytology in Meyer's ' Geschichte der 

 Botanik,' i. p. 120. 



