I at once recognized in that of the apparition, rendered yet more
distressing by the feminine and beautiful features upon which it rested.

"I am not naturally superstitious; but, shaken and clouded as my mind
had been by the use of opium, I could not wholly divest it of fear when
these phantoms beset me. Yet, on all other occasions, save that of
their immediate presence, I found no difficulty in assigning their
existence to a diseased state of the bodily organs, and a corresponding
sympathy of the mind, rendering it capable of receiving and reflecting
the false, fantastic, and unnatural images presented to it.

[One of our most celebrated medical writers considers spectral
illusion a disease, in which false perceptions take place in some
of the senses; thus, when the excitement of motion is produced in a
particular organ, that organ does not vibrate with the impression
made upon it, but communicates it to another part on which a
similar impression was formerly made. Nicolai states that he made
his illusion a source of philosophical amusement. The spectres
which haunted him came in the day time as well as the night, and
frequently when he was surrounded by his friends; the ideal images
mingling with the real ones, and visible only to himself. Bernard
Barton, the celebrated Quaker poet, describes an illusion of this
nature in a manner peculiarly striking:--

"I only knew thee as thou wert,
A being not of earth!
"I marvelled much they could not see
Thou comest from above
And often to myself I said,
'How can they thus approach the dead?'