174 Decomposition of Carbonic Acid by Solar Light. 



in the total resulting volume, the quantities that had been 

 evolved in three successive periods of examination from the 

 beginning to the termination of the experiment were, 

 1st period, 21*8 per cent, of nitrogen. 

 2nd ... 18-8 

 3rd ... 26-0 



During the progress of this decomposition, therefore, more 

 nitrogen relatively was evolved towards the close of the ex- 

 periment than at its beginning. 



From this result, therefore, I again infer that the nitrogen 

 emitted by leaves is derived from the decomposition of some 

 azotized body, and not from air mechanically included in their 

 pores. 



The following are the experimental results which I have 

 obtained : — 



1st. That the nitrogen comes from the tissue of the leaf 

 itself; because more than three times as much is evolved from 

 bicarbonate of soda as is imprisoned in the structure of the 

 leaf, removable by the air-pump. 



2nd. In twelve hours, from bicarbonate of soda, leaves will 

 evolve more than five times their own volume of gaseous 

 matter. 



3rd. The quantity of nitrogen in the composition of leaves 

 is sufficient for furnishing all the nitrogen obtained in the gas 

 evolved. From Boussingault's analyses it appears that they 

 contain nearly ten times the required amount. 



4th. The decomposition of some nitrogenized constituent 

 of the leaf is essential to the appearance of the nitrogen ; there 

 is no other available source. 



At this stage of the inquiry a remarkable analogy appears 

 between the function of digestion in animals, and the same 

 function in plants. Liebig has shown how, from the trans- 

 formation of the stomach itself, food becomes acted upon and 

 is turned into chyme ; an obscure species of fermentation 

 brought about by the action of nitrogenized bodies. So, in 

 like manner in plants, the decay of a nitrogenized body is in- 

 timately connected with the assimilation of carbon, for, as I 

 have stated, the process here under discussion is a true di- 

 gestion, and not a respiratory process. And as there are 

 facts which seem to show that the primary action of the light 

 is not upon the carbonic acid, but upon the nitrogenized fer- 

 ment, the decomposition of the gas ensuing as a secondary re- 

 sult, is it not probable that chlorothyl is the body which in 

 vegetables answers to the chyle of animals ? The oxygen, which 

 disappears during the decomposition of carbonic acid, disap- 

 pears to bring about the eremacausis of the nitrogenized body. 

 And have not the gum, the starch, the lignin, and other car- 



