The principles which the study of the Nerves of Sensation and of Voluntary Motion within the Orbit is thought to illustrate, are:—

1. The peculiarity of the muscles of the Eyeball, that they receive few or no sensitive filaments, such as supply all other muscles of the body,—coupled with the peculiarity of their office, that they are designed, in the natural state, to be regulated, not by sensations excited in themselves by their action, but by sensations excited thereby in the Retina,—suggests an important reflection on the use of sensitive nerves and of sensations in guiding and regulating all voluntary and instinctive muscular motion; the sensations which result from the commencing action in every case fixing the effort of the will on the right muscles, and regulating the extent to which the contractions shall be carried; while experience in some cases, and instinct in others, teaches what motor nerves must act, in order to excite the commencement of these sensations.