The dream, then, is subject-matter for psychology; and the first question that we have to ask about it concerns its make-up; _of what mental processes is the dream composed_? The answer is twofold. So far as _pattern_ goes, anything whatsoever may appear in the dream-state: perception, memory, emotion, imagination, thought, everything. But as regards the _mental processes_ themselves, the dream is selective; certain processes are preferred for dreaming, so to say, as certain processes are preferred for the representation of self. The details of dreams are very quickly forgotten; and there is always danger lest recall and report, in the waking state, change the terms of a dream, translate them from their original mode into the customary terms of waking experience. We have, however, a large number of records, taken under favourable conditions, and we find substantial agreement among the various observers. Dreams are mainly visual, though lights are more and colours are less common, perhaps, than is ordinarily supposed. Next in order of frequency to vision stands audition; conversation, especially, is a common feature of dreams. Next follow sense-feelings and feeling-attitudes; unpleasant experiences seem, on the whole, to be more frequent than pleasant, though there are marked individual differences. Thereafter, at a wide remove, come touch and kinæsthesis and organic complexes; and last of all, taste and smell. We know so little of the nervous correlates of the dream that a discussion of these facts must of necessity be speculative. It has been said that we dream largely in terms of sight for the same reason that we remember and imagine largely in those terms (‘dream’ is, for that matter, the older English word for ‘imagine’): the eye is the most important of all the sense-organs, the organ most continuously used, and the organ most relied upon for knowledge of the outside world; hence the visual centre of the brain has multitudinous connections with all the other brain-centres, and is readily excited when any one of them is excited. It has been pointed out, also, that the eye is extremely sensitive to slight changes of illumination, as well as to changes in the pressure of the eyelids, the state of circulation in the retina, and so forth; and that the sensations thus set up are reinforced by the persistent central grey. Observation has proved that the figures of a dream-scene may roughly correspond with the dots and splashes of light and colour that you see over the dark field of vision just before you fall asleep. So in regard to hearing: it may be said that verbal perceptions and ideas are, in the waking life, subordinate in number and importance only to those of vision; and it may be said, also, that the ear is the great defensive organ of the night-time, so that ear-sleep (if we may coin the word) is rarely profound, and the ear is liable to excitation by any chance crack or