Other authors have been content to render prominent one or another of the tangible psychological peculiarities of the dream life, and perhaps to take these as a starting point for more far-reaching attempts at explanation. It has been justly remarked that one of the main peculiarities of the dream life appears even in the state of falling asleep, and is to be designated as the phenomenon inducing sleep. According to Schleiermacher[61] (p. 351), the characteristic part of the waking state is the fact that the psychic activity occurs in ideas rather than in pictures. But the dream thinks in pictures, and one may observe that with the approach of sleep the voluntary activities become difficult in the same measure as the involuntary appear, the latter belonging wholly to the class of pictures. The inability for such presentation work as we perceive to be intentionally desired, and the appearance of pictures which is regularly connected with this distraction, these are two qualities which are constant in the dream, and which in its psychological analysis we must recognise as essential characters of the dream life. Concerning the pictures—the hypnogogic hallucinations—we have discovered that even in their content they are identical with the dream pictures. The dream therefore thinks preponderately, but not exclusively, in visual pictures. It also makes use of auditory pictures, and to a lesser extent of the impressions of the other senses. Much is also simply thought or imagined (probably represented by remnants of word presentations), just as in the waking state. But still what is characteristic for the dream is only those elements of the content which act like pictures, _i.e._ which resemble more the perceptions than the memory presentations. Disregarding all the discussions concerning the nature of hallucinations, familiar to every psychiatrist, we can say, with all well-versed authors, that the dream hallucinates, that is, replaces thoughts through hallucinations. In this respect there is no difference between visual and acoustic presentations; it has been noticed that the memory of a succession of sounds with which one falls asleep becomes transformed while sinking into sleep into an hallucination of the same melody, so as to make room again on awakening, which may repeatedly alternate with falling into a slumber, for the softer memory presentations which are differently formed in quality.