Emotion and Imagination--How Stimuli are transformed into Emotion--Somnambulism--The Failure of Movement in Dreams--Nightmare--Influence of the approach of Awakening on imagined Dream Movements--The Magnification of Imagery--Peripheral and Cerebral Conditions combine to produce this Imaginative Heightening--Emotion in Sleep also Heightened--Dreams formed to explain Heightened Emotions of unknown origin--The fundamental Place of Emotion in Dreams--Visceral and especially Gastric disturbance as a source of Emotion--Symbolism in Dreams--The Dreamer's Moral Attitude--Why Murder so often takes place in Dreams--Moral Feeling not Abolished in Dreams though sometimes Impaired. Whether the influences which stimulate our dreams arise from without or from within the organism, they are always filtered and diffused through the obscured channels of perception. They reach the brain at last in a vague and massive shape which may or may not betray to waking analysis the source from which they arise, but will certainly have become so changed in these organic channels that their affective tone will be predominant. They are, that is to say, largely transformed into _emotion_. And, when so transformed, they become the origin of what we regard as the imaginative element in dreams.[75] Sleep is especially favourable to the production of emotion because while it allows a considerable amount of activity to sensory activities, and a very wide freedom to the imagery founded on sensory activities, it largely and in many directions inhibits motor activity. The actions suggested by sensory excitation cannot, therefore, be carried out. As soon as the impulse enters motor channels it is impeded, broken up, and scattered in a vain struggle. This process is transmitted to the brain as a wave of emotion. Sometimes, indeed, as we know, motor co-ordinations, usually inhibited in sleep, are not so inhibited. The dreamer is able to execute, perfectly or imperfectly, some action which, really or in imagination, he desires to execute. He is then said to be in a state of somnambulism. The somnambulist, in the wide sense of the word, is not necessarily a person who walks in his sleep, but any person in whom a group of co-ordinated muscles is sufficiently awake to respond more or less adequately to the motor impulse from the sleeping brain. To talk in sleep is a form of somnambulism. When the motor channels are thus unimpeded, there is usually no memory of a dream on awaking. The impulses that reach consciousness can be, as it were, quickly and easily drained off to the surface of the nervous system, and they tend to leave no deep impress on consciousness.