It will be noticed in these cases that although the perception has its origin centrally, in the mind itself, and is even voluntarily produced, still, it is seen as an impression made upon the visual organ in exactly the same manner as a picture thrown upon the retina by a real external object; it disappears when the eyes are closed or an opaque object intervenes, and follows the laws of optics in general; hence, strictly speaking, these perceptions are also real. (2) Perceptions may have their origin _peripherally_--that is, the point of excitation which causes the act of perception in the mind may exist in the external sense organs themselves, even when no external object corresponding to the perception exists at the time, or it is not in a position on account of distance or intervening objects to affect the senses. In examining the cases which may be placed under this head they resolve themselves into two classes: those which occur in connection with some disease or defect in the sense organ concerned, and those which are recrudescences or after-visions, arising from over-excitation of those organs; for instance, after looking through a window in a very bright light--even a considerable length of time afterwards--on shutting the eyes or looking into a dark room, an image of the window is seen with all its divisions and peculiarities of construction distinctly presented. To the country lad returning home at night from his first visit to the circus the whole scene is again presented; and ring, horses, equestrians, acrobats and clowns are all seen and externalized with the utmost distinctness; even the crack of the ring-master's whip is heard and the jokes and antics of the clowns repeated. (3) Perceptions may have their origin telepathically--that is, scenes and incidents transpiring at a distance far too great to affect the bodily organs of sense in any direct or ordinary way do, nevertheless, in some way, cause perceptions to arise in the mind corresponding to those same scenes and incidents. This is comparatively a new proposition in psychology and has for its basis studies and experiments which have only been systematically made within the past fourteen years. These studies and experiments relate to telepathy, automatism, and the action of the subliminal self. They have been undertaken and carried on by various societies interested in experimental psychology, but chiefly by the English Society for Psychical Research, some of the results of whose labors have been briefly sketched in the preceding chapters. In addition to the reports of these societies an important contribution to the subject of apparitions was published by the then secretaries of the Society for Psychical Research, the late Mr. Edmund Gurney, Mr. Frederick W. H. Myers, and Mr. Frank Podmore.