Dr Alison on the Principle of Vital Affinity. 289 



attaches itself to the elements of water, always present where 

 vegetables grow, and so forms various compounds, beginning 

 with the varieties of starch ; in all which it is the principal in- 

 gredient. The compounds thus formed next attack and par- 

 tially decompose the water, and appropriate the hydrogen, 

 thus causing a farther evolution of oxygen, and forming oil ; 

 and afterwards nitrogen, in small quantity, is introduced, and 

 fresh transformations take place, by which the protein com- 

 pounds 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 pro- 

 portion than that ; and the formation of these may be confi- 

 dently 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 pro- 

 portion 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 ci- 

 tricl2C8H140 = 9C + 8HO + 3C02, the malic 8 C 6H 

 10O = 6C + 6HO-f2CO2, the tartaric 8C 4H 10 = 50 + 

 4H0 + 3C02,tlie oxalic 4C2H 80 = + 2 HO + 300 J 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 orga- 

 nized 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 inorganic 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 com- 

 pounds, in which the characteristic predominance of carbon 

 is not perceived ; because they are those which are formed in 

 circumstances where the vital affinities are losing their power. 



