However true this may be, is not meat nevertheless something different from limestone, although limestone may easily be found that contains nearly all the elements present in the meat? In starch, sugar, fat, etc., precisely the same elements enter as in water and carbonic acid, but no materialist denies that there are important differences between these two groups of substances.
What is it, then, that essentially separates the two classes of matter (nothing but the most essential factors concerns us here)? If we ask this question of chemistry, we are answered that this quality is combustibility. Organic matter is combustible; inorganic is not.
But why should organic matter be combustible? Because fuel is as necessary to the organism as to the steam engine. To both their physical source of power is heat, and even the engine receives it through the combustion of organic substances. All the fuel that is generally used is of organic origin, although we seldom think of this fact.
But why can we not fire an engine with inorganic products? Because these cannot burn, and the reason again is, that they are already burned. If this be true, they must once have been fuel themselves, must once have been in a burning state. How do we know this? Because the inorganic world consists almost entirely of chemical compounds that are only formed by combustion, when this word is used in its widest sense.
If these suggestions are correct, organic matter is to inorganic as fuel to the products of combustion. In the inorganic world the latter have been transformed to fuel which in a renewed combustion reproduces the same products as those of which it once was formed.
If this be the case our problem may be thus formulated: Can inorganic products of combustion again form combustibles spontaneously? Can carbonic acid or water through the spontaneous activity of physical forces be transformed into sugar, starch, fat, etc.?
In order to decide if this be possible we must first know what combustion is, and we will therefore briefly explain what this term means.
Combustion is a chemical process, it is said, and this definition may be true, although it may also be misleading. In daily speech combustion is generally identified with the phenomena of light and the generation of heat, which we immediately observe, but chemical processes can neither be seen nor felt, because they take place in the inner world of matter which hitherto has proved inaccessible to human observation. Yea, chemical processes are so foreign to the experiences of our senses that chemistry, the science of these processes, is entirely founded on the deductions of our reason. The premises that our reason uses for its conclusions belong to the physical world which is the outer side of matter that faces us. The phenomena that accompany combustion belong to this world and are, therefore, strictly speaking, not chemical but physical phenomena.
But even if these phenomena of light and heat, of which the latter especially interests us here, belong to the world comprehensible to our senses, they must nevertheless be intimately connected with the inner chemical process because heat is developed in nearly every chemical reaction. Heat is not created from nothing; there must be a cause for this force, and the cause cannot be anything but the chemical energy which in the chemical process is transformed into heat. In few words: What we generally term combustion cannot be identical with the actual chemical process. The light and the heat must, on the contrary, be considered as the external results of the chemical process, its physical effect.
By a close study of this physical effect we have also been able to explain what happens within matter itself. As it is necessary to understand this in order to comprehend how heat is developed, we will endeavor shortly to outline the present scientific conception of the chemical process called combustion.