58 OF THE ASSIMILATION OF CARBON. 



the opposite result shows that the question was false- 

 ly stated, and that the conception 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 do not 

 suggest more correct ideas in the place of those 

 which it is intended to refute, it should be disre- 

 garded ; because the worse experimenter the critic 

 is, the greater will be the discrepancy between the 

 results he obtains and the views proposed by the 

 other. 



It is too much forgotten by physiologists, that their 

 duty really is not to refute the experiments of others, 

 nor to show that they are erroneous, but to discover 

 truth, and that alone. It is startling, when we re- 

 flect that all the time and energy^ of a multitude of 

 persons of genius, talent, and knowledge, are ex- 

 pended in endeavors to demonstrate each other's 

 errors. 



The question whether carbonic acid is the food of 

 plants or not has been made the subject of experi- 

 ments with perfect zeal and good faith ; the results 

 have been opposed to that view. But how was the 

 inquiry instituted ? 



The seeds of balsamines, beans, cresses, and 

 gourds, were sown in pure Carrara marble, and 

 sprinkled with water containing carbonic acid. The 

 seeds sprang, but the plants did not attain to the 

 development of the third small leaf. In other cases, 

 they allowed the water to penetrate the marble from 

 below, yet, in spite of this, they died. It is worthy 

 of observation, that they lived longer with pure dis- 

 tilled water than with that impregnated with carbon- 

 ic acid ; but still, in this case also, they eventually 

 perished. Other experimenters sowed seeds of plants 

 in flowers of sulphur and sulphate of barytes, and 

 tried to nourish them with carbonic acid, but without 

 success. 



Such experiments have been considered as positive 

 proofs, that carbonic acid will not nourish plants ; 



