In the further synthesis of organic compounds the problems we have before us are of the same order as those already solved. There is no essential difference between organic and inorganic chemistry; living organisms are formed of the
same elements as the mineral world, and the organic combinations of these elements may be realized in our laboratories, just as in the laboratory of the living organism.
Not only so, but a living being only borrows for a short time those mineral elements which, after having passed through the living organism, are returned once again to the mineral kingdom from which they came.
All matter has life in itself—or, at any rate, all matter susceptible of incorporation in a living cell. This life is potential while the element is in the mineral state, and actual while the element is passing through a living organism.
Mineral matter is changed into organic matter in its passage through a vegetable organism. The carbonic acid produced by combustion and respiration is absorbed by the chlorophyll of the leaves under the stimulus of light—the oxygen of the carbonic acid being returned to the air, while the carbon is utilized by the plant for the formation of sugar, starch, cellulose, and fats.
Thus plants are fed in great part by their leaves, taking an important part of their nourishment from the air, while by their roots they draw from the earth the water, the phosphates, the mineral salts, and the nitrates required for the formation of their albuminoid constituents. A vegetable is a laboratory in which is carried out the process of organic synthesis by which mineral materials are changed into organic matter. The first synthetic reaction is the formation of a molecule of formic aldehyde, CH2O, by the combination of a molecule of water with an atom of carbon.
From this formic aldehyde, or formol, we may obtain all the various carbohydrates by simple polymerization, i.e. by the association of several molecules, with or without elimination of water. Thus two molecules of formol form one molecule of acetic acid, 2CH2O = C2H4O2. Three molecules of formol form a molecule of lactic acid, 3CH2O = C3H6O3. Six molecules of formol represent glucose and levulose, 6CH2O = C6H12O6. Twelve molecules of formol minus one molecule of water form saccharose, lactose, cane sugar, and sugar of milk, 12CH2O = C12H22O11 + H2O; n times six
molecules of formol minus one molecule of water, n(C6H10O5), form starch and cellulose.
Animals derive their nourishment from vegetables either directly, or indirectly through the flesh of herbivorous animals. The mineral matter, rendered organic in its passage through a vegetable growth, is finally returned by the agency of animal organisms to the mineral world again, in the form of carbonic acid, water, urea, and nitrates. Thus vegetables may be regarded as synthetic agents, and animals and microbes as agents of decomposition. Here also the difference is only relative, for in certain cases vegetables produce carbonic acid, while some animal organisms effect synthetic combinations. Moreover, there are intermediary forms, such as fungi, which possessing no chlorophyll are nourished like animals by organic matter, and yet like vegetables are able to manufacture organic matter from mineral salts.
The work of combustion begun by the animal organism is finished by the action of micro-organisms, who complete the oxydation—the re-mineralization of the chemical substances drawn originally from the inorganic world by the agency of plant life.