it remains to make
a few comments on them.

The weirdness of visions lies in their sudden appearance, in their
vividness while present, and in their sudden departure. An incident
in the Zoological Gardens struck me as a helpful simile. I happened
to walk to the seal-pond at a moment when a sheen rested on the
unbroken surface of the water. After waiting a while I became
suddenly aware of the head of a seal, black, conspicuous, [12] and
motionless, just as though it had always been there, at a spot on
which my eye had rested a moment previously and seen nothing. Again,
after a while my eye wandered, and on its returning to the spot the
seal was gone. The water had closed in silence over its head without
leaving a ripple, and the sheen on the surface of the pond was as
unbroken as when I first reached it. Where did the seal come from,
and whither did it go? This could easily have been answered if the
glare had not obstructed the view of the movements of the animal
under water. As it was, a solitary link in a continuous chain of
actions stood isolated from all the rest. So it is with the visions;
a single stage in a series of mental processes emerges into the
domain of consciousness. All that precedes and follows lies outside
of it, and its character can only be inferred. We see in a general
way that a condition of the presentation of visions lies in the
over-sensitiveness of certain tracks or domains of brain action and
the under-sensitiveness of others, certain stages in a mental
process being represented very vividly in consciousness while the
other stages are unfelt; also that individualism is changed to
dividualism.

[Footnote 12: See some curious correspondence on this subject in
the _St. James' Gazette_, Feb. 10, 15, and 20, 1882.]

I do not recollect seeing it remarked that the ordinary phenomena of
dreaming seem to show that partial sensitiveness is a normal
condition during sleep. They do so because one of the most marked
characteristics of the dreamer is the absence of common sense. He
accepts wildly incongruous visions without the slightest scepticism.
Now common sense consists in the comprehension of a large number of
related circumstances, and implies the simultaneous working of many
parts of the brain. On the other hand, the brain is known to be
imperfectly supplied with blood during sleep, and cannot therefore
be at full work. It is probable enough, from hydraulic analogies,
that imperfect irrigation