To grow big is not everything: activity is essential. The scraps will be repeated, it is true, but always so sparingly and at such distant intervals that we begin to wonder what part eating really plays in this instance. My prisoners, large and small, subjected to a strict fast, give especial cause for reflection. Whenever I disturb their repose—and my curiosity deprives itself of few opportunities—they move about briskly, brandishing their tails, delving the sand, sweeping it, shifting it; in short, they expend many kilogram-metres of energy, to use the technical expression; and this goes on for eight or nine months. In performing this work what do they expend on materials? Nothing. From the first day of their imprisonment all food is cut off. The thought occurs to the mind of nutritive reserves, of adipose savings accumulated in the organism. The animal, according to this, in order to balance the expenditure of energy, would live upon itself. With portly adults the explanation would be valid in a certain measure; but I have subjected lean specimens, of medium age, to the test; I have selected young ones, just beginning life. What can these small Scorpions have in their bellies? What do they possess that can be transformed into motor energy by vital oxidation? The scalpel cannot find it and the imagination refuses to appraise it, so great is the disproportion between the amount of work accomplished and the worker’s bulk. If the whole animal were before all a combustible and were to burn to the last atom, the total sum of heat emitted would still be far from equivalent to the total sum of the mechanical effects. Our factories cannot keep an engine going, all the year round, with a lump of coal as its whole provision. My Scorpions hardly seem to consume even this lump of fuel. After a long and rigorous abstinence, they are as fresh and brightly-coloured, as glossy with health as at the beginning of the experiment. We can understand the Snail, sunk in a deep inertia and contracted within his shell, whose opening he has closed with a chalky lid or a parchment cover: he no longer eats, but neither does he see; he exists on his reserves by slowing down his vital processes to the lowest possible limits. The Scorpion, always moving about, despite the excessive prolongation of the fast, is beyond our comprehension.