This simple case of the formation of hydrocarbons from the elements furnished by carbonic acid and water is only adduced as an illustration of the general principle. The modes by which the power of the sun actually takes effect in the decomposition of stable compounds, and the formation of unstable ones from the elements thus obtained, are innumerable, and the processes as well as the combinations that result are extremely complicated. These processes include not only the first formation of the unstable compounds in the leaf, but also an endless series of modifications and re-arrangements which they subsequently undergo, as well in the other organs of the plant as in those of the animal when they are finally introduced into an animal system. In all, however, the general result is substantially the same—namely, the forcing of elements into unnatural combinations, so to speak, by the power of the sun acting through the instrumentality of vegetation, in order that they may subsequently, in the animal system, give out that power again by the effort they make to release themselves from the coercion imposed upon them, and to return to the natural unions in which they can find again stability and repose.
One of the chief elements employed in the formation of these weakly-combined substances is nitrogen—its compounds being designated as nitrogenous substances, and noted, as a class, for the facility with which they are decomposed. Nitrogen is, in fact, the great weak-holder of nature. Young students in chemistry, when they learn that nitrogen is distinguished by the weakness of its affinities for other elements, and its consequent great inertness as a chemical agent, are often astonished to find that its compounds—such as nitric acid, nitre, which gives its explosive character to gunpowder, nitro-glycerine, gun-cotton, and various other explosive substances which it helps to form—are among the most remarkable in nature for the violence and intensity of their action, and for the extent to which the principle of vitality avails itself of them as magazines of force, upon which to draw in the fulfillment of its various functions.
186 GENTLE MEASURES.
But this is really just what should be expected. It is the very weakness of the hold which nitrogen maintains upon the elements combined with it that facilitates their release, and affords them the opportunity to seize with so much avidity and violence on those for which they have a strong attraction.
It is as if a huntsman should conduct a pack of ferocious dogs into a field occupied by a flock of sheep, quietly grazing, holding the dogs securely by very strong leashes. The quiet and repose of the field might not be seriously disturbed; but if, on the other hand, a child comes in, leading the dogs by threads which they can easily sunder, a scene of the greatest violence and confusion would ensue.
In the same manner, when nitrogen, holding the particles of oxygen with which it is combined in the compounds above named by a very feeble control, brings them into the presence of other substances for which they have a very strong affinity, they release themselves at once from their weak custodian, and rush into the combinations which their nature demands with so much avidity as to produce combustions, deflagrations, and explosions of the most violent character.
The force which the elements display in these reunions is always—and this is one aspect of the great discovery of modern times in respect to the persistence or constancy of force which has already been referred to—precisely the same in amount as that which was required for dissevering them from their original combinations with such substances at some previous time. The processes of vegetation are the chief means employed for effecting the original separations, by the power of the sun, and for forming the unstable compounds by which this power is held in reserve. The animal system, on the other hand, takes in these compounds, remodels them so far as is required to adapt them to its structure, assimilates them, and then, as occasion requires quires, it releases the concealed force, which then manifests itself in the forms of animal heat, of muscular motion, and of cerebral and nervous power.
In what way, and to what extent, the knowledge of these truths should influence us in the management and training of children in respect to their extraordinary activity, is the question we have next to consider.
Practical Applications of these Principles.
If we watch a bird for a little while hopping along upon the ground, and up and down between the ground and the branches of a tree, we shall at first be surprised at his incessant activity, and next, if we reflect a little, at the utter aimlessness and uselessness of it. He runs a little way along the path; then he hops up upon a twig, then down again upon the ground; then "makes believe" peck at something which he imagines or pretends that he sees in the grass; then, canting his head to one side and upward, the branch of a tree there happens to strike his eye, upon which he at once flies up to it. Perching himself upon it for the moment, he utters a burst of joyous song, and then, instantly afterwards, down he comes upon the ground again, runs along, stops, runs along a little farther, stops again, looks around him a moment, as if wondering what to do next, and then flies off out of our field of view. If we could follow, and had patience to watch him so long, we should find him continuing this incessantly changing but never-ceasing activity all the day long.