Organisms as automatically regulated energy-transforming machines

In The Dynamics of Living Matter (1906), Loeb contrasted artificial machines, whose energy is supplied by the hand of man, with machines that arise in nature.² He held that the natural ones endure only when the energy supply is regulated automatically. His first example was the waterfall, which he described as a machine turning distance energy into kinetic energy and heat. Its permanency rests on the physical conditions that keep water flowing to the cataract.² His second example was the green plant, a machine that turns radiating energy into chemical energy.³ He said its permanency is guaranteed by an automatic arrangement, the growth of stems toward the light, which he called heliotropism.⁴

Other authors framed the same problem differently. Verworn (1899) described vital motion, or metabolism, as a complex motion that sharply marks the living organism.¹ He doubted that such a motion had run unbroken from the incandescent masses of the early earth, which Preyer had counted as alive.¹ Driesch (1908) separated two parts of the second principle of energetics. The first is a principle of becoming: nothing can happen without diversities, and new diversities need earlier ones.⁵ The empirical part, in his view, was only that intensities must differ, and that an intensity can only be raised when another intensity falls.⁵

Leduc (1911) set the waterfall inside a general account of energy. He treated energy as the product of a quantity and an intensity. The intensity is a difference of position or condition, such as the height of a weight or a difference of electric potential. He wrote that without such a difference there is no current of energy, and so no change from one form to another.⁶ He defined any mechanism that passes one form of energy into another as a transformer. He then placed every living being, man included, in that class, changing energy from earth, air and sun into motion, nervous energy and heat.⁷

Lillie (1923) grouped whirlpools, candle flames and waterfalls as systems with a constant configuration. In them, intake of material and energy from outside balances the disintegration their own activity causes. He wrote that, as with living organisms, their integrity depends on continual and balanced interchange with the surroundings.⁸ Lotka (1925) set waterfalls within the inorganic cycle of water, citing Henderson's estimate that evaporation from 100 square kilometers of tropical ocean amounts to over one hundred million horsepower.⁹ Loeb stressed automatic regulation of supply. Lillie stressed balanced exchange.