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Living bodies are immersed in physical conditions as in a sea. External agencies–light, moisture, air, gravity, mechanical and chemical influences–cause great changes in them; but their power to adapt themselves to these changes, and profit by them, remains unexplained. Are morphological processes identical with chemical ones?

In the inorganic world we everywhere see mechanical adjustment, repose, stability, equilibrium, through the action and interaction of outward physical forces; a natural bridge is a striking example of the action of blind mechanical forces among the rocks. In the organic world we see living adaptation which involves a non-mechanical principle. An adjustment is an outward fitting together of parts; an adaptation implies something flowing, unstable, plastic, compromising; it is a moulding process; passivity on one side, and activity on the other. Living things struggle; they struggle up as well as down; they struggle all round the circle, while the pull of dead matter is down only.

Behold what a good chemist a plant is! With what skill it analyzes the carbonic acid in the air, retaining the carbon and returning the oxygen to the atmosphere! Then the plant can do what no chemist has yet been able to do; it can manufacture chlorophyll, a substance which is the basis of all life on the globe. Without chlorophyll (the green substance in plants) the solar energy could not be stored up in the vegetable world. Chlorophyll makes the plant, and the plant makes chlorophyll. To ask which is first is to call up the old puzzle, Which is first, the egg, or the hen that laid it?

According to Professor Soddy, the engineer’s unit of power, that of the British cart-horse, has to be multiplied many times in a machine before it can do the work of a horse. He says that a car which two horses used to pull, it now takes twelve or fifteen engine-horse to pull. The machine horse belongs to a different order. He does not respond to the whip; he has no nervous system; he has none of the mysterious reserve power which a machine built up of living cells seems to possess; he is inelastic, non-creative, non-adaptive; he cannot take advantage of the ground; his pull is a dead, unvarying pull. Living energy is elastic, adaptive, self-directive, and suffers little loss through friction, or through imperfect adjustment of the parts. A live body converts its fuel into energy at a low temperature. One of the great problems of the mechanics of the future is to develop electricity or power directly from fuel and thus cut out the enormous loss of eighty or ninety per cent which we now suffer. The growing body does this all the time; life possesses this secret; the solar energy stored up in fuel suffers no loss in being transformed into work by the animal mechanism.

Soddy asks whether or not the minute cells of the body may not have the power of taking advantage of the difference in temperature of the molecules bombarding them, and thus of utilizing energy that is beyond the capacity of the machinery of the motor-car. Man can make no machine that can avail itself of the stores of energy in the uniform temperature of the earth or air or water, or that can draw upon the potential energy of the atoms, but it may be that the living cell can do this, and thus a horse can pull more than a one-horse-power engine. Soddy makes the suggestive inquiry: “If life begins in a single cell, does intelligence? does the physical distinction between living and dead matter begin in the jostling molecular crowd? Inanimate molecules, in all their movements, obey the law of probability, the law which governs the successive falls of a true die. In the presence of a rudimentary intelligence, do they still follow that law, or do they now obey another law–the law of a die that is loaded?” In a machine the energy of fuel has first to be converted into heat before it is available, but in a living machine the chemical energy of food undergoes direct transformation into work, and the wasteful heat-process is cut off.