Carbon in Organic Beings. 207 



built up by retaining the carbon, and the oxygen is 

 restored to the air. It combines with various sub- 

 stances to form salts so directly useful to man, that 

 we can hardly regard them as other than a special 

 provision for him. But before the creation of man, 

 it played an important part in the animal kingdom. 

 Nearly all the shell-fish and coral animals that filled 

 the old oceans of geologic ages, like those that are 

 now piling up their walls and towers among the 

 waves, built their masonry of carbonate of lime. The 

 1 beds of limestone and the quarries of marble 

 arc the products of carbonic acid gas. 



Like the other elements already mentioned, car- 

 bon has a perfect fitness for its place in the animal 

 tissue. In partial decomposition of the tissues, it 

 forms soluble compounds, and finally it beconu 



with such relations to the blood, the tissue of 

 the lung and the air, that it is constantly set free 

 ir<>m the system, while oxygen takes its place to 

 produce the changes necessary for the continuance 

 of life. We do not pretend to understand fully all 

 those changes, notwithstanding our advance in ani- 

 mal chemistry ; but we understand the results per- 

 fectly. We see carbon making a large part of our 

 food. \Ye know that carbon is consumed in the 

 body by oxidization. We know that heat is pro- 

 duced, and that the compounds of carbon are such, 

 that this element is as rapidly and easily eliminated 

 from the body when it has done its work in the vital 

 processes, as those elements that are permanent 

 gases. We find it then a body with great diversity 



