CONSTRUCTIVE KESULTS OF DEOXIDATION. 51 



the leaves are now covered all over with minute beads of gas, and 

 that a small but appreciable quantity of gas has collected at the 

 top of the cylinder. By pulling the attached thread I am able to 

 withdraw the bunch of mint, and on now passing up a few 

 bubbles of nitric oxide, a dark-brown vapour is produced at the 

 top of the cylinder, proving the contained gas to be oxygen ; 

 which oxygen, gradually evolved by the growing plant, has been 

 separated by the plant from the carbonic acid, or hydrated oxide 

 of carbon, wherewith it was surrounded. 



(50.) Now, just as oxidation tends to break up the constituent 

 carbon and hydrogen atoms of a complex organic molecule 

 into simpler and simpler bodies, so, on the other hand, do 

 we find that deoxidation tends to combine the separated carbon 

 and hydrogen atoms into more and more complex bodies. 

 The organism of a plant, for instance, operating upon mono- 

 carbon molecules only, effects simultaneously their deoxidation 

 and inter-combination. It deoxidates them with evolution of 

 oxygen into the atmosphere, and combines the residual less 

 oxygenated carbon and hydrogen into the various forms of vege- 

 table tissue and secretion. What the intermediate stages are 

 between water and carbonic acid, on the ono hand, and some 

 vegetable principle such as mannite or sugar on 'the other, we can- 

 not positively say, though our knowledge upon the subject is re- 

 ceiving daily accessions. But be our acquaintance with the 

 intermediate stages ever so imperfect, the final result is perfectly 

 intelligible. We know, for instance, that in the production of this 

 body, mannite, there has been a deoxidation of six molecules of 

 carbonic anhydride and seven molecules of water, and that in the 

 course of the deoxidation, the thirteen separate molecules have 

 been conjoined into one single molecule, thus : 



Carb-anhydride Water- Oxygen Mannite 



6 CO, + 7 H a O - 130 = i CsH^Oe 



(51.) This, then, is the point which I wish to bring promi- 

 nently under your notice that while oxidation tends to the sepa- 

 ration of atoms, and the formation of simple out of complex 



E2 



