Just as an electric spark or a flash of lightning which lasts the one-thousandth part of a second leaves an impression in us a hundred times longer; just as our eye is unable to follow the different positions of a burning brand swung round in the dark, but sees, as it were, a ribbon of fire; just as we burn our hand when we touch a glowing object before we have time to feel the pain; just as, when in movement, we often stumble against obstacles which confront us without our having time to stop; so the impressions which reach the nerve-centres keep us agitated for some time without our having the force to stand still midway on the declivity down which the sudden impetus of the emotion is speeding us. We have all experienced this inability of the organism, we know that we do not succeed in subduing even the slightest mental perturbations. Suppose a person is walking quietly along, when suddenly he sees before him the figure of a man whom he was trying to avoid. At once his blood begins to boil. Scarcely, however, has he seen the man before he becomes aware that he has made a mistake, and he is glad; but his heart has already begun to beat more vigorously, the perturbation and oppression do not at once subside, but continue to annoy for some time. They are like the continued vibrations of a cord that has been shaken, like a flame shooting up as the spark disturbs the equilibrium of the molecules in the nerve-centres, like the echo of a sound reverberating in the nervous fibres and slowly dying away. IV What is the last expression of pain, the last manifestation of sensibility? This is a question we must study in order to learn the relative importance of the phenomena making up the picture of fear, and to see which of these offer the most lengthened resistance in the struggle with death. By means of chloral or alcohol I have produced such a profound sleep in dogs or rabbits that they could not rouse themselves again. One cannot imagine a quieter decease, a gentler and more gradual sinking of the organism into the arms of death. As soon as a strong dose of chloral or alcohol has been administered, the animal becomes somewhat excited, the hind legs begin to give way; when we call him he cannot turn without falling; he rises, makes another attempt, totters, turns round, falls again, rises with difficulty, and finally lies down stretched out and tranquil. From time to time he tries to raise his head and then falls into a leaden sleep. The respiration is slower, the temperature gradually falls, at length the wagging of the tail ceases. The lids droop over the sleepy eyes, the face is tranquil, the ears motionless, whatever pain the efforts made to awaken him may cause. One might think he was dead. The only method which physiologists had of finding out whether an animal in this condition was still capable of feeling was by investigating whether the heart and blood-vessels still responded to painful stimuli.