IECT. I* iNf ROStrsCEPTION. 



consequence was that it very soon died. He then 

 introduced a plant by the root and stem only, 

 while the leaves were still exposed to the influence 

 of the air. But in this case the plant lived much 

 longer than in the former, and warranted him, as 

 he thought, to conclude that leaves are the lungs 

 of plants. It is plain., however, that this conclusion 

 was by much too hasty ; because the life of the 

 plant might have been protracted merely by the 

 absorption of the moisture of the atmosphere 

 through the medium of the leaf, and not by the 

 inhalation of any gaseous principle. And before 

 venturing upon such a conclusion, the experiment 

 should have been also reversed, to show the result 

 of enclosing the leaves only in the receiver, and of 

 leaving out the stem and root : and if it had even 

 been proved that atmospheric air is actually inhaled 

 by the leaf and indispensable to the health of tlie 

 plant, still it would have been necessary to show 

 that it is again expired also, in order to make good 

 the analogy of leaves to lungs. 



Another argument in support of the doctrine 



was deduced from Du Hamel's experiment of 



besmearing the surface of the leaf with oil, in 



consequence of which treatment it soon died, 



owing, as it appeared, to the exclusion of air.* 



But this argument is also insufficient to establish 



the fact, and is here introduced, together with that 



of M. Papin, not merely for the purpose of show- 



* Phys. des Arb. liv. ii. chap. iii. 



H 2 



