Fevers are very often accompanied by frightful dreams. According to Moreau (de la Sarthe),[96] their occurrence indicates that the attack will be long, and that there is probably some organic affection present. My own experience agrees with that of Macario,[97] to the effect of not confirming these opinions. I have, however, generally observed that the frequency and intensity of the morbid dreams were in proportion to the severity of the fever.
Diseases of the heart are very generally attended with disagreeable dreams. They are usually short, and, as Macario remarks, relate to approaching death. The patient starts from sleep in terror, and sometimes it is difficult to convince him of the reality of his visions.
Dyspepsia and other diseases of the intestinal canal often give rise to morbid dreams. They are usually accompanied by a sense of impending suffocation, and ordinarily consist of frightful images, such as devils, demons, strange animals and the like. The presence of worms in the intestines is likewise a frequent cause of such dreams.
In chlorosis dreams are very common. Occasionally they are of a pleasant character, but in the majority of cases they are the reverse of this.
It would be difficult to mention a disease which is not, at some time or other of its career, an exciting cause of morbid dreams. The most interesting examples, however, are met with in cases of insanity and other cerebral affections, and frequently the delusions of the dreams are so mixed up with those which arise during the waking condition, that the patient is unable to separate them and to determine which are the consequence of erroneous sensations received when awake, and which are the results of dreams. The careful examination of almost any insane persons will also show that they incorporate the fancies of their dreams with the realities of everyday life. Indeed, the relations of dreaming to insanity are so interesting and important as to have attracted the marked attention of alienists and psychologists.
Cabanis[98] gives Cullen the credit of being the first to point out the similarity between the phenomena of dreaming and those of delirium, and himself enters at length into the full discussion of the several questions involved. A very little reflection will suffice to convince the reader that the two conditions are strikingly alike. In dreams we never distinguish the false from the real; the judgment, if exercised at all, acts in the most erratic manner; we are rarely surprised at the occurrence of the most improbable circumstances; our characters for the time being often undergo a radical change, and we perform imaginary acts in our sleep which are altogether at variance with our actual dispositions. The hallucinations of sleep we accept as realities just as the insane individual believes in all the erroneous impressions made upon his senses. The dreaming person is, in fact, the victim of delusions which, during the existence of his condition, have a firm hold on his mind and render him in no essential particular different from the one who suffers from mental unsoundness. The incoherence present in dreams, and the evident dependence of the various images upon the suggestion of previous images, are likewise phenomena of the insane state.
Even in persons perfectly sane, dreams often produce a very powerful influence on the mind. Most of us have, on awaking, felt pleased or disturbed from reflecting upon the circumstances of a dream we have had during the night, and occasionally the impression has remained through the entire day. With children this influence is still more strongly shown. As Sir Henry Holland[99] remarks, the corrections from reason and experience are less complete in them than in adults. As a consequence, they not infrequently confuse their dream-visions with the facts of their lives, and regard the former as real events. The hallucinations of dreams are also occasionally continued during wakefulness, and hence some persons have, on awaking, seen the images which had been present to them in their sleep.
The celebrated Benedict de Spinoza[100] was once the subject of an illusion which had its starting-point in a dream. He dreamed that he was visited by a tall, thin, and black Brazilian, diseased with the itch. He awoke, and thought he saw such an image standing beside him.
Muller,[101] in referring to such instances, says:
“I have myself also very frequently seen these phantasms, but am now less liable to them than formerly. It has become my custom when I perceive such images, immediately to open my eyes, and direct them upon the wall or surrounding objects. The images are then still visible, but quickly fade. They are seen whichever way the head is turned, but I have not observed that they moved with the eyes. The answers to the inquiries which I make every year of the students attending my lectures as to whether they have experienced anything of the kind, have convinced me that it is a phenomenon known to comparatively few persons. For among a hundred students, two or three only, and sometimes only one, have observed it. This rarity of the phenomena is, however, more apparent than real. I am satisfied that many persons would perceive these spectres if they learned to observe their sensations at the proper times. There are, however, undoubtedly many individuals to whom they never appear, and in my own case they now sometimes fail to show themselves for several months at a time, although in my youth they occurred frequently. Jean Paul recommended the watching of the phantasms which appear to the closed eyes as a means of inducing sleep.”