Of all the human cases I have studied, the observations made on this boy gave me the greatest trouble. As I had to do with an idiot, the least obstacles became great difficulties. No apparatus could be applied without his becoming restless, snatching it from his head, and breaking everything which fell into his hands. I had to confine myself to a few observations which could be made by surprising him while asleep. But he did not sleep regularly; I have often found him still awake, even when I made my nightly visit at a very late hour. It was more than sleeplessness, it was a nocturnal excitement, which presaged the storm of an epileptic attack. I have seen him the victim of the most terrible fits, while, on the nights following, his sleep was so deep as to leave one in doubt whether it was a natural phenomenon. In the period of exhaustion and stupor, the blood-vessels of the brain seemed to relax, and at every contraction of the heart the pulsations became stronger. A faint noise which did not wake the patient was enough to produce a change in the brain and a more abundant gush of blood. It sufficed to touch him, or to approach him with the lamp: immediately, the volume of the brain increased, and a great elevation appeared in the curve of the pulse. Whenever we called him by name, it seemed as though an impetuous wave of blood rushed into the brain, causing the convolutions to swell. As this was invariably the case, there could be no doubt that the brain was still sensitive to the impressions of the external world, even during a heavy sleep. When the patient was shaken till he woke, I could see the circulation changing little by little, as though the material conditions of consciousness were being restored. He often spoke a few indistinct words, opened his eyes, or moved his hands, and then slowly fell back into the previous stupor, while we saw the pulse grow weaker, the brain decrease in volume, the rhythm and force of the breathing change. It was one of the most interesting sights to observe in the stillness of night, by the light of a little lamp, what was going on in his brain, when there was no external cause to disturb this mysterious life of sleep. The brain-pulse remained for ten or twenty minutes quite regular and very weak, and then began suddenly, without any apparent cause, to swell and beat more vigorously. Then the agitation subsided and there was a second period of quiet; then came stronger blood-waves which flooded the convolutions, raising the height of the pulsations, which were automatically marked by the apparatus applied to the brain. We scarcely dared breathe. The one who was observing the instruments communicated with the other, who was watching over the patient, by pressing his hand. Looks full of interrogation and wonder would meet, and exclamations had to be forcibly repressed.