346 
the alkalies, and earths, with mineral acids, ge- 
nerally abound in soils. From the decomposition 
of basaltic, porphyritic, and granitic rocks, there is a 
constant supply of earthy, alkaline, and ferruginous 
materials to the surface of the earth. In the sap of all 
plants that have been examined, certain neutro-saline 
compounds, containing potash, or soda, or iron, have 
been found. From plants they may be supplied to 
animals. And the chemical tendency of organiza- 
tion seems to be rather to combine substances into 
more complicated and diversified arrangements, than 
to reduce them into simple elements *." To these 
views of the economy of living beings we yield our 
cordial assent, and hold them to be not less consis- 
tent with the most advanced state of chemical sci- 
ence, than with the justest conceptions we can form 
of the varying structure and properties of organic 
beings. They lead us directly back to the opinion, 
that vegetables derive the carbonaceous matter 
that contributes to their growth through the fluids 
which they absorb from the situations in which they 
grow* 
652. IN the same manner as the carbonic matter is 
exhaled by plants, so likewise have we maintained 
that, during the continuauce of living action, it is 
given off by the exhalent function of animals. The 
facts which we adduced in support of this opinion 
* Phil. Trans. 1808, p. 33, .34. 
