Spinoza and Jean Paul Richter both experienced this survival of dream-images.

Still more pertinent is the fact that the effects of retinal fatigue are producible by dream-images.

The physiologist Gruithuisen had a dream, in which the principal feature was a violet flame, and which left behind it, _after waking_, for an appreciable duration, a complementary image of a yellow spot.[84] Subjective auditory sensations appear to be much less frequent causes of dream-illusions than corresponding visual sensations.

Yet the rushing, roaring sound caused by the circulation of the blood in the ear is, probably, a not uncommon starting-point in dreams.

With respect to subjective sensations of smell and taste, there is little to be said.