681. This can be still more clearly evident to us from the objects of our sight, to which mental imagery or a material idea almost answers on its own plane. In any object of the eyesight taken as a single entity, when it is looked at through the microscope there appear thousands of things of which it is composed. Thus a hundred tiny insects take up but one ray of vision, appearing as one point, and a faint one at that; while to the artificial or optically aided sight, not only a hundred little living animals are revealed, but even the internal parts of each.