It is highly probable that hypnagogic pictures are identical with the dream-pictures of normal sleep--forming their visual foundation. Maury[46] has proved from self-observation that the pictures which hovered around him hypnagogically were also the objects of the dreams that followed. G. Trumbull Ladd[47] has shown this even more convincingly. By practice he succeeded in waking himself suddenly two to five minutes after falling asleep. He then observed that the figures dancing before the retina at times represented the same contours as the pictures just dreamed of. He even states that nearly every visual dream is shaped by the retina's own light-figures. In our case the fantastic rendering of these pictures was favoured by the situation. We must not underrate the influence of the over-excited expectation which allowed the dull retina-light to appear with increased intensity.[48] The further formation of the retinal appearances follows in accordance with the predominating presentations. That hallucinations appear in this way has been also observed in other visionaries. Jeanne d'Arc[49] first saw a cloud of light, and only after some time there stepped forth St. Michael, St. Catherine and St. Margaret. For a whole hour Swedenborg[50] saw nothing but illuminated spheres and fiery flames. He felt a mighty change in the brain, which seemed to him "release of light." After the space of one hour he suddenly saw red figures which he regarded as angels and spirits. The sun visions of Benvenuto Cellini[51] in Engelsburg are probably of the same nature. A student who frequently saw apparitions stated: "When these apparitions come, at first I only see single masses of light and at the same time am conscious of a dull noise in the ears. Gradually these contours become clear figures."
The appearance of hallucinations occurred in a quite classical way in Flournoy's Helen Smith. I quote the cases in question from his article.[52]
"18 Mars. Tentative d'expérience dans l'obscurité. Mlle. Smith voit un ballon tantôt luminieux, tantôt s'obscurcissant.
"25 Mars. Mlle. Smith commence à distinguer de vagues lueurs, de longs rubans blancs, s'agitant du plancher au plafond, puis enfin une magnifique étoile qui dans l'obscurité s'est montrée à elle seule pendant toute la séance.