CHAP, ii.] of Plants. Van Helmoht. 455 



According to Aristotle's view the plant itself was quite pas- 

 sive in the work of nutrition ; since food was offered to it which 

 had been already prepared for it in the earth, growth was to 

 some extent merely a process of crystallisation unaccompanied 

 by chemical change. In pointing to the formation of excreta 

 Jung on the contrary ascribed a chemical activity to the plant, 

 and by supposing that the organisation of the root was such 

 as to prevent the entrance of certain matters and to favour that 

 of others, he made the plant co-operate in its own nourish- 

 ment, though he did not assume that it needed a thinking soul 

 for this purpose. 



Johann Baptist van Helmont 1 , physician and chemist, and a 

 contemporary of Jung, took up a position still more decidedly 

 opposed to Aristotelian doctrines. He rejected the four 

 elements of that philosophy, and regarding water as a chief 

 constituent of all things he considered that the whole substance 

 of plants, the mineral parts (the ash) as well as the combustible, 

 was formed from water. Thus while Aristotle made the com- 

 ponent parts of plants be introduced into them by water in a 

 state ready for use, Van Helmont, on the contrary, ascribed to 

 the plant the power of producing all kinds of material from 

 water. It would scarcely have been necessary to mention this 

 resistance to old dogmas, originating as it did in the notions of 

 the alchemists, if Van Helmont had not made an attempt to 

 establish his views by experiment ; this was the first experiment 

 in vegetation undertaken for a scientific purpose of which we 

 have any information, and it was repeatedly quoted by many 

 later physiologists, and employed in support of their theories. 

 He placed in a pot a certain quantity of earth, which when 

 highly dried weighed two hundred pounds ; a willow-branch 



1 J. B. van Helmont was born at Brussels in 1577, and died at Villvorde 

 near Brussels in 1644. He was a leading representative of the chemistry of 

 his day. Kopp, in his ' Geschichte der Chemie,' i&43, i. p. 117, has given 

 n. full account of his life and labours. 



