522 Theory of the Nutrition [BOOK in. 



a prisoner within that circle of ideas, and he made a much 

 freer use of the vital force than De Candolle ; he went even 

 farther than this, and in his want of chemical experience he 

 hit upon the grossly materialistic notion of a vital matter 

 (I. p. 6). This vital matter is a half-fluid substance, which 

 may be obtained from all bodies that were once alive by 

 boiling and by decay ; it is formed from other elements, but it 

 is itself the true elementary matter with which alone physi- 

 ology has to do ; it is common to the animal and vegetable 

 kingdom, and is purest when in the form of mucilage, albumen, 

 and gelatine ; that animals and plants alike consist of this vital 

 matter explains the circumstance, that plants serve as food for 

 animals and animals as food for plants. He goes on to show 

 that a similar unctuous substance, called by chemists extract of 

 the soil, and considered by many of them to be an important 

 ingredient in the nutrition of plants, is their true and proper 

 food. This extract of the soil was therefore the vital matter 

 which plants take up; it was natural that Treviranus should no 

 longer attribute any importance to the decomposition of 

 carbon dioxide in the leaves, especially as he was unable to 

 understand the chemical connection of all that Ingen-Houss, 

 Senebier, and de Saiissure had written. He explained the co- 

 operation of light in the nutrition of plants to be a merely 

 ' formal condition,' and the salts in solution in the water of the 

 soil were in his opinion stimulants for the use of the extremities 

 of the roots, which were thus put into a condition of 'vital 

 turgescence ' ; and as the functions of the leaves, such as 

 Malpighi and Hales had conjectured, and Ingen-Houss, Sene- 

 bier, and de Saussure had proved it to be, had no existence for 

 Treviranus, he made the assimilation of the soil-sap take place 

 on its way, as it flowed upwards and downwards through the 

 plant. We see that nothing can be conceived more deplorable 

 than this theory of nutrition ; it would have been bad at the 

 end of the i;th century, it is difficult to believe that it could 

 have been published thirty years after de Saussure's work. 



