to this the remarkable circumstance that although we hear with two ears, the sensibility of which is often very different, yet we never hear a sound double, as we often see things double with our two eyes, we are led to the conjecture that the sensation of hearing does not arise in the labyrinth or in the cochlea, but deep in the brain where the two nerves of hearing meet, and thus the impression becomes simple. But this is where the pons Varolii encloses the medulla oblongata, thus at the absolutely lethal spot, by the injury of which every animal is instantly killed, and from which the nerve of hearing has only a short course to the labyrinth, the seat of acoustic vibration. Now it is just because its source is here, in this dangerous place, in which also all movement of the limbs originates, that we start at a sudden noise; which does not occur in the least degree when we suddenly see a light; for example, a flash of lightning. The optic nerve, on the contrary, proceeds from its thalami much further forward (though perhaps its source lies behind them), and throughout its course is covered by the anterior lobes of the brain, although always separated from them till, having extended quite out of the brain, it is spread out in the retina, upon which, on stimulation by light, the sensation first arises, and where it is really localised. This is shown in my essay upon sight and colour. This origin of the auditory nerve explains, then, the great disturbance which the power of thinking suffers from sound, on account of which thinking men, and in general all people of much intellect, are without exception absolutely incapable of enduring any noise. For it disturbs the constant stream of their thoughts, interrupts and paralyses their thinking, just because the vibration of the auditory nerve extends so deep into the brain, the whole mass of which feels the oscillations set up through this nerve, and vibrates along with them, and because the brains of such persons are more easily moved than those of ordinary men. On the same readiness to be set in
