For instance, whenever anyone desires to look at a remote object, the act of volition causes the pupil of the eye to dilate, whereas, if the person in question had only thought of the dilatation of the pupil, the mere wish to dilate it would not have brought about the result, inasmuch as the motion of the gland, which serves to impel the animal spirits towards the optic nerve in a way which would dilate or contract the pupil, is not associated in nature with the wish to dilate or contract the pupil,