OF CARBON. 45 



veins in their return to the heart from different 

 parts of the body, and is exhaled in the state 

 of carbonic acid gas; and this gas so exhaled, 

 is, of course, unfit for respiration until the car- 

 bon it contains is absorbed in some way or 

 other from the oxygen. 



Now it is calculated* that a man consumes 

 every day, in the usual course of respiration, 

 45,000 cubic inches of oxygen gas ; that a thou- 

 sand millions of men consume in one year 

 rffVo of all the oxygen that exists in the atmo- 

 sphere: and hence, in the course of time, all 

 this gas, the prime necessary of life, would be 

 entirely consumed, if some corrective power 

 did not exist to neutralize this effect. For this 

 power we must look to plants. It has been ex- 

 plained that the gas exhaled from the lungs of 

 all animals is carbonic acid gas — that is, car- 

 l)on combined with oxygen — and we are now 

 ill a position to prove that plants absorb all this 

 carbonic acid gas. That they assimilate the 

 carbon to themselves, and give up the oxygen 

 in a pure state again to support animal life, 

 and again to enter into the state of carbonic 

 acid, and again to be purified in the vegetable 

 structure, and thus to perform its office in an 

 unceasing round of useful operations. 



In the calculations here submitted, all notice 

 of the quantity of carbon emitted by animals, 

 or in the process of combustion is omitted — 

 and yet these sources supply a quantity of 

 carbon considerably greater than those we have 



* Lfebig. 



5* 



