OBJECT OF EXPERIMENTS IN PHYSIOLOGY. 37 



nature from those in which oxalic acid is formed. 

 Vitality, in its peculiar operations, makes use of a 

 special apparatus for each function of an organ. A 

 rose twig engrafted upon a lemon-tree, does not 

 bring forth lemons but roses. Vegetable physiolo- 

 gists in the study of their science have not directed 

 their attention to that part of it which is most 

 worthy of investigation. 



The second cause of the incredulity with which 

 physiologists view the theory of the nutrition of 

 plants by the carbonic acid of the atmosphere is, 

 that the art of experimenting is not known in phy- 

 siology, it being an art which can be learned accu- 

 rately only in the chemical laboratory. Nature 

 speaks to us in a peculiar language, in the language 

 of phenomena ; she answers at all times the ques- 

 tions which are put to her ; and such questions are 

 experiments. An experiment is the expression of 

 a thought : we are near the truth when the pheno- 

 menon, elicited by the experiment, corresponds to 

 the thought ; while the opposite result shows that 

 the question was falsely stated, and that the con- 

 ception was erroneous. 



The critical repetition of another's experiments 

 must be viewed as a criticism of his opinions ; if 

 the result of the criticism be merely negative, if it 

 dcSfnot suggest more correct ideas in the place of 

 those which it is intended to refute, it should be 

 disregarded ; because the worse experimenter the 

 critic is, the greater will be the discrepancy between 



