I will make but one observation upon this singular phenomenon, and that is, that it particularly concerns the nerves of motion, and hardly ever affects the nerves of sensation. In fact we know, that in wounds of the head, in consequence of apoplexy, &c. one eye, one ear, one side of the tongue, one nostril, do not become insensible, as the muscles of one side cease to move. We do not suddenly become paralytic on one side as it regards sensation, as we do as it respects motion in hemiplegia. Experiments cannot elucidate this, for it is impossible to perceive the alterations of sensibility as we do those of mobility. However, by compressing the brain of a dog, and thus rendering him paralytic on one side, and then shutting each eye separately and alternately, to see if he distinguished objects, and afterwards by presenting in turn to each nostril volatile ammonia, or other pungent substances, I have not seen, as it regarded the sensibility, an alteration corresponding with that which the mobility experienced. We often observe in man a discordance in the organs of sense. One ear hears better than the other, one eye sees further, &c.; hence false hearing, hence a species of strabismus, &c.; but the cause of these discordances appears to reside in the organ itself, and not to be connected with the brain. Moreover, it does not appear that each hemisphere always corresponds necessarily with the nerves of motion of the opposite side. In fact, we often see on the right side effusions or injuries of the cerebral substance, without any alterations of motion on the left, and vice versa.