The application of the new knowledge to the elucidation of many obscure diseases, where the nervous system was affected, engaged Charles Bell’s zealous attention. He speedily classified and arranged cases illustrative of the action of the motor and sensory nerves, cases where the muscles of the face were paralysed, as well as various kinds of paralysis throughout the body. Instances of partial or local pain were explained in their relation to the nerves concerned; disorders of the eye, tongue, muscles of respiration, &c., all received new illumination from his researches. A further discovery was that of the muscular sense, by which we perceive many of the qualities of objects surrounding us, and which even enables us to stand upright. The sensation of the degree of muscular effort put forth in every action, in every resistance, to a large extent builds up our judgments about external objects, and determines our actions; and the recognition of the fact that we perceive this by a sense distinct from touch is due to Bell. The study of the eye entered very largely into this question, as the muscular movements of the eye are of such extreme import in our perceptions. In 1818 he wrote: “I think I have made out that squinting depends on the over-action of one of the oblique muscles, and that it may be cured by an operation. I am looking out for a patient to try this upon.” But for want of a squinting monkey to make the first trial upon, the thought was not carried to practical results, and it remained for others to mature the operation for the cure of squinting.