21 



and quite as little with those I have endeavoured to diffuse on 

 this subject ; so that a more detailed elucidation of the state- 

 ments from which these results are drawn is quite necessary. 



M. Dutrochet complains of those botanists, who think that 

 animal life has nothing in common with that of plants ; ac- 

 cording to his opinion, with which in so far I entirely agree, 

 life is not different in its fundamental phaenomena in all be- 

 ings. It has frequently been admitted, that those phaeno- 

 mena, which in vegetables are comprehended under respira- 

 tion, are exactly opposed in their results to the respiration of 

 animals : M. Dutrochet does not take this view, but accord- 

 ing to him the respiration in plants consists as in animals in 

 a fixation of the oxygen, while I have endeavoured to show in 

 my Physiology (ii. p. 150.), that the respiration of plants, like 

 that of animals, consists in a carbonization of substance, as in 

 both oxygen is inspired and carbonic acid expired. 



In examining the organs of plants which carry on the pro- 

 cess of respiration, M. Dutrochet relates the opinions of 

 MM. Link and Amici, according to which the spiral vessels 

 and their appendages should be regarded as the pneumatic 

 apparatus of vegetables. However M. Link is not at all of this 

 opinion in his recent works, but states that aggregations of 

 air are even found in the intestinal canal of animals, yet this 

 exists for very different purposes. The conveyance of air is 

 evinced very decidedly in the cells of the pith, and nothing 

 can be more certain than that the medulla serves to convey 

 and elaborate the absorbed sap for the young shoots. M. Du- 

 trochet was formerly of opinion that the large spiral vessels in 

 the wood of the vine conducted the nutritive sap, and even at 

 the present time considers this to be correct, but thinks that 

 it is to be attributed solely to this cause, that so long as the 

 leaves are wanting, no transpiration is indicated, and that the 

 sap consequently collects in the spiral vessels. 



The spiral vessels are therefore said to be the pneumatic 

 organs in the wood, while distinct large cells are found in 

 the bark conveying air, which are supposed to be situated in 

 the interior of the bark, and to communicate one with the 

 other. I must confess that I have no idea of these cells, which 

 are said to carry on the process of respiration in the interior 

 of the bark, wholly leaving out of view, that it is not probable 



