
THE PRINCIPLE OF VITAL AFFINITY. 187 
starch from carbonic acid and water has been completed, and effecting a decom- 
position of part of the water, as well as of the carbonic acid, presented to the 
living vegetable. . 
In studying this first and most striking of all the changes which are to be 
ascribed to vital affinities, it is especially necessary to understand the parts as- 
signed to Carbon and Oxygen; and, in taking this general view, we must regard 
vegetables and animals as inseparably linked together, and look to the whole 
series of chemical changes which intervene between the origin of vegetables and 
the death and decomposition of animals. We must regard the carbon, originally 
existing in combination with oxygen in the atmosphere, in the proportion of one 
equivalent to two, as the great agent employed by Nature in the formation of the 
whole organized creation, insomuch that all organic chemistry may be said to be 
the chemistry of compounds of carbon.—(Gregory’s Chemistry, p. 241.) That it 
may fulfil this office it is invested with peculiar but temporary powers; it is se- 
parated at particular points and under certain conditions from the oxygen, and 
attaches itself to the elements of water, always present where vegetables grow, 
and so forms various compounds, beginning with the varieties of starch; in ali 
which it is the principal ingredient. The compounds thus formed next attack and 
partially decompose the water and appropriate the hydrogen, thus causing a far- 
_ ther evolution of oxygen, and forming oil; and afterwards nitrogen, in small quan- 
| tity, is introduced, and fresh transformations take place, by which the protein 
compounds are formed. All the solid structures of vegetables, and indeed of 
_ organized beings generally, are made up of these compounds of carbon, in which 
_ oxygen exists either in the proportion to hydrogen which forms water, or in a 
_ less proportion than that ; and the formation of these may be confidently ascribed 
to vital affinities. But it is easy to conceive that other compounds of carbon with 
_ hydrogen and oxygen will exist in plants in which the oxygen will be in larger 
proportion than this, without supposing oxygen from the air to be added; because 
_ the vital affinities may not have been in sufficient force to separate the oxygen 
_ completely from its original union with carbon, and these, therefore, may be re- 
_ garded as compounds of carbon, water, and undecomposed carbonic acid. Such 
| are the different organic acids (the citric 12C 8H 140=9 C+8 HO+3CO,, the 
| malic 8C 6H 100=6C+6HO+2CO., the tartaric 8C 4H 100=5C+4 HO 
+3 CO,, the oxalic 4 C 2H 8 O=C+2 HO+3 CO.) which are found in the juices 
| of many vegetables, particularly in the immature state. 
Again, it is always to be observed, not only that all organized bodies are 
destined ultimately to revert to the water, carbonic acid, and ammonia, from 
| which they were originally formed, but that, in the case of animals at least, there 
| is a process always going on during the state of life, by which these same inor- 
| ganic matters are continually evolved from the living frames. Therefore, we 
| cannot be surprised to find that the fluids of all living animal bodies contain other 
