Theory of the Nutrition [BOOK in. 



thus the best results of the observations of Ingen-Houss, 

 Senebier, and de Saussure were lost upon the German veget- 

 able physiologists. 



6. SETTLEMENT OF THE QUESTION OF THE FOOD-MATERIAL 

 OF PLANTS. 1840-1860. 



WE have noticed in the previous section the rise of views 

 during the period between 1830 and 1840 which were calculated 

 to make the hypothesis of a vital force appear superfluous, at 

 least as an explanation of certain important phenomena in 

 vegetation ; such were the referring the natural heat of plants 

 to chemical processes, and the movement of the sap to osmose ; 

 in the domain of chemistry also, in which Berzelius had in the 

 year 1827 made the distinction between organic and inorganic 

 matter to consist in the fact, that the former is produced under 

 the influence of the vital force, the opinion was openly expressed 

 that such an intrusion of the vital principle could not be 

 allowed, since organic compounds had been repeatedly pro- 

 duced from inorganic substances by artificial means, and 

 therefore without its aid. The general tendency of scientific 

 thought was now in fact unfavourable to the nature-philosophy 

 of former days ; it inclined to free itself from the obscurity 

 that attended the idea of a vital force, and to assert the belief, 

 that chemical and physical laws prevail alike outside and inside 

 all organisms; this idea became an axiom with the more 

 eminent representatives of natural science after 1840, and if 

 not always expressed in words, was made the basis of all their 

 attempts to explain physiological phenomena. 



Thus a freer course began to open for the intellectual 

 movement of the time even before the year 1840, and strict 

 inductive research, and above all the establishment of facts 

 and closer reasoning were now demanded in the question of 

 the nutrition of plants, as they were also in the domain of 

 morphology and phytotomy. But in dealing with the theory 



