nal relations between them, but having the same
emotional stamp,--joyous, melancholy, erotic, etc. This form of
association is very frequent in dreams and reveries, i.e., in a state
of mind in which the imagination enjoys complete freedom and works
haphazard. We easily see that this influence, active or latent, of the
emotional factor, must cause entirely unexpected grouping to arise, and
offers an almost unlimited field for novel combinations, the number of
images having a common emotional factor being very great.

There are unusual and remarkable cases with an exceptional emotional
base. Of such is "colored hearing." We know that several hypotheses have
been offered in regard to the origin of this phenomenon.
Embryologically, it would seem to be the result of an incomplete
separation between the sense of sight and that of hearing, and the
survival, it is said, from a distant period of humanity, when this state
must have been the rule; anatomically, the result of supposed
anastamoses between the cerebral centers for visual and auditory
sensations; physiologically, the result of nervous irradiation;
psychologically, the result of association. This latter hypothesis seems
to account for the greater number of instances, if not for all; but, as
Flournoy has observed, it is a matter of "affective" imagination. Two
sensations absolutely unlike (for instance, the color blue and the
sound _i_) may resemble one another through the equal retentive quality
that they possess in the organism of some favored individuals, and this
emotional factor becomes a bond of association. Observe that this
hypothesis explains also the much more unusual cases of "colored" smell,
taste, and pain; that is, an abnormal association between given colors
and tastes, smells, or pains.

Although we meet them only as exceptional cases, these modes of
association are susceptible to analysis, and seem clear, almost
self-evident, if we compare them with other, subtle, refined, barely
perceptible cases, the origin of which is a subject for supposition, for
guessing rather than for clear comprehension. It is, moreover, a sort of
imagination belonging to very few people: certain artists and some
eccentric or unbalanced minds, scarcely ever found outside the esthetic
or practical life. I wish to speak of the forms of invention that permit
only fantastic conceptions, of a strangeness pushed to the extreme
(Hoffman, Poe, Baudelaire, Goya, Wiertz, etc.), or surpr