Dreams of flying, associated at times with dreams of falling, are probably the commonest of dreams. Usually they leave behind them a distinct remembrance of a pleasurable nature. So impressed have been some individuals with the reality of the flying sensation that they have essayed to fly when awake, futilely of course, and sometimes with disastrous results. In the flights the dreamer does not seem to fly high, usually a few feet above ground or over the heads of pedestrians for a distance of about twenty feet. Sometimes the flights are over high hills, as in the case of a lady acquaintance of the writer. To her it seems as if she flies pleasurably and easily over a high hill, falls pleasurably and gracefully to the bottom, and then flies over the next hill In modern times flights in aeroplanes are becoming common, even in those who have never made an actual flight.

Many explanations have been given for the flying dream. The most popular is that it is due to the rhythmic rising and falling of the chest, which becomes conscious by reason of some slight interference with normal respiration. Sleep seems to be especially favourable for suggesting aviatory powers. The respirations are shallower than in the waking state, and more thoracic in character. Mild interruptions of the normal respiratory rate, which are not unusual in sleep, may thus suggest the dream.

Mosso1 has stated: "When we sleep it is especially the diaphragm which reposes; with some persons the abdomen is almost motionless in sleep, but a slight noise or push, a voice, or any external action suffices to make it resume its functions, and the diaphragmatic breathing becomes more active. This takes place suddenly, without our waking, and without any recollection of it remaining in consciousness." According to Shepard,2 with the oncoming of sleep there is a decrease in the amplitude of the abdominal breathing movements and relative increase in the chest movements. In sleep three types of breathing, with intermediate forms, are distinguished. The first is shallow, slow breathing, alternating with a period of deeper, freer, and more rapid breathing, beginning abruptly, the alternation showing in chest and abdomen. The second is intermediate between the extremes of the first type, but with the chest movements deeper than in the waking state. The third is regular, deep breathing. Stimuli during the first two types gave increased amplitude, sometimes with a slower, sometimes with a faster rate, and always with an increase in the abdominal movements. Stimuli during the third type gave a period of shallower and faster movements, as a rule.

1 Op. cit, p. 122.

2 The Circulation and Sleep, 1914, p. 38. The Macmillan Co.

It has been suggested that some dreams of flying may be due to a slight alteration of cardiac action. The heart has a period of contraction, the systole, that is comparable to expiration; and a period of relaxation, the diastole, comparable to inspiration. In some instances, persons awake from a dream of flying conscious of some palpitation of the heart; in a case known to the writer, there was a feeling of gas in the stomach. The change in the cardiac rate may be due to many causes, as indigestion, emotions resulting from a dream, etc. The same causes which may provoke an increased respiratory rate may also increase the cardiac action, and the increase usually occurs in both organs simultaneously, or nearly so. In waking life we can note that an increased respiratory rate increases the rate of the heart. While dreams of flying are to be regarded without concern as a rule, prudence dictates that a physician be consulted should they occur very often, especially if they are accompanied by a sensation of cardiac uneasiness.

As pointed out by Ellis, and others, respiratory activity alone will not wholly account for the flying dream. In addition to the sense of lightness caused by the increased, superficial breathing, one would have to lose the awareness of contact with the bed. The sense of contact with the earth is ever present, else we would feel light and seem to rise in air. In certain nervous diseases, as hysteria, where there is a numbness of the skin, the sensation of lightness and rising in air is often experienced in the waking state. In sleep, the feeling that one is no longer in contact with the bed may be brought about by numbness of the skin due to lying in one position for a long time. Coldness is a possible cause. It is known that the body temperature varies at different periods of the day; it is lowest in the early morning hours. A combination of disturbed respiratory activity and numbness of the skin are, therefore, to be regarded as the main features in causing most dreams of flying.

An understanding of the psychology of suggestion and of the causes of flying dreams will help us to understand many fanatics who from time to time assert that they have the ability to fly without exterior aid. Many hysterics, of a religious trend, believing in their own ability to fly, have filled many of their disciples with the same idea, and have predicted that on a certain day they and their followers would fly to Heaven. Those who have essayed to do so usually found the services of a physician necessary. Epileptics sometimes have the sensation of lightness and of rising in air. A former patient of the writer's asserted that just prior to a convulsion she felt as if she rose "right to Heaven." The sensation of rising also occurs to some dying persons, leading often to the idea that they are being carried to Heaven. One individual's dying words: "Don't let them take me; keep me down," were probably occasioned by this sensation. With death there is an increase in, and a lightness of respiration, plus a numbness of the skin, the parts furthest removed from the head becoming numb first.