The question of movement in dreams, of the presence or absence of effort and inhibition, is thus seen to be explicable by reference to the depth of sleep and the particular groups of centres involved. In full normal sleep movements are purely ideatory, and no difficulty arises in executing any movement, for the reason that there really is no movement at all, or even any attempt at movement, while, even if slight movement occurs, no message of its actual defectiveness can reach the brain. Movement or attempt at movement, with more or less inhibition, tends to occur when the motor and sensory centres are in a partially aroused state; it is a phenomenon which belongs to the period immediately before awakening.[82] It is doubtless mainly due to the diffusion of inhibited nervous impulses through many channels, and the vague and massive character which they hence assume in consciousness, that we must attribute the magnification of dream imagery, and the exaggeration of dream feelings. This is not a constant tendency of our dreams; sometimes, indeed, perhaps in special stages of sleep-consciousness, there is diminution, and people look no larger than dolls, and houses like doll's houses, while, on the emotional side, events which in real life would overwhelm us, may, in dreams, be accepted as matters of course. But the heightening of imagery and ideas and feelings is very common. There is a kind of normal megalomania in our dreams. We have already incidentally encountered many instances of this: a tooth appears large enough for a mouse to play in, or like a great jagged rock; the irritation of a mosquito evokes the image of a huge scarlet beetle; in vesical dreams endless streams are seen to flow; a canary's song is heard as Haydn's _Creation_, and the howling of the wind becomes a chanted Te Deum. A French author has written an impressive literary description of his own purely visual dreams, with their magnificent exaggerations and joyous expansiveness, seeking to show that their chief character is their excessiveness; 'the flowers are almost women.'[83] I cannot, however, recognise this as characteristic of normal dreaming. It bears more resemblance to De Quincey's opium dreams, or to the visions which came to Heine as he listened to Berlioz's music. In normal dreaming the imagery may, indeed, be stupendously vast, or fantastically absurd, or poignantly intense. But normal dreams are not built on a consistently colossal scale. The megalomania of dreaming is only accidental and occasional, not systematic.[84]