cipient chaos. It is at this
point that images are really most intense, and that every idea assumes a
body and form, every image a reality: finally, when the body and the
brain have reached the physiological conditions of sleep, thoughts which
had been changed into hypnagogic images in the intermediate stage
between sleep and waking, are altogether transformed into the real
images of dreams.

By an effort of will I have often been able to surprise myself in this
intermediate stage, and the same thing has been done by others, and it
always appears that this is the real moment of transition from
wakefulness to dreaming, I have been able to verify the fact that the
first dream is only the continuation of our last waking thoughts, which
have now become dramatic and real I have also observed that this
intermediate stage between waking and dreaming, during which the images
are real and vivid, although we are still conscious of our real
condition, goes on for a long while, sometimes for a whole night, with
brief intervals of sleep. This has occurred to me when I was kept awake,
either when travelling at night, or when I had taken a large draught of
water before lying down (other liquids or food does not produce the
phenomenon) or if I have been looking during the day at objects
illuminated by dazzling sunshine. In all these circumstances the bright
and vivid images appear reduced to an almost microscopic scale, although
very distinct in form and colour; in ordinary cases, the images appear
of the ordinary size, but not without a tendency to become smaller.

I believe that there is a physical cause for the reduction and
attenuation of the images in the excessive excitement of the retina, or
central encephalic organ in which images are formed in conscious
concurrence with the cortical part of the hemispheres. Owing to the
excitement caused by wakefulness, by fatigue, by sunshine, or in some
cases by the condition of the nerves of the stomach, the objective
projection on psychical space, partly transmitted by heredity and
gradually formed by associations and local signs,[34] is arrested by the
innate force of the image on the organ, and it appears to be smaller and
in proportion with the relative smallness of the image which is produced
by minute vibrations and by the susceptibility of the cellule. This
intermediate and persistent stage of hypnagogic images serves in every
way to explain the physical genesis of involuntary hallu