The analogies which exist between hallucinations in dreams and in a waking condition, have induced writers who look on hallucination as a pathological phenomenon, to place the two in the same category. An English writer who maintains this doctrine, says that, in both cases, the horses draw the chariot without a guide, with this difference, that the coachman is drunk in insanity, and asleep in dreams, † Here, in fact, lies the difference.

More recently, MM. Moreau and Al. Maury, have maintained a similar opinion. If this be admitted, the result would be that none would escape insanity, since those whom it would spare during the day would be attacked in the night. The absolutism of this proposition is its best refutation. The dreaming state, in an immense majority of cases, is a purely physiological condition; it is merely a continuation of the action of the intelligent principle; and to establish the truth of this proposition, it would be only necessary to bring forward any of the plans and actions which are conceived and executed during sleep. We may, therefore, conveniently classify dreams into two divisions, according as they are physiological or pathological.

* Grand Dictionnaire des Sciences Medicales, t. xxxiv. art. Incube; case communicated by Dr. Parent. † The Antiquary, vol. i. p. 189.

The conditions of sleep necessarily modify nocturnal hallucinations. In fact, in dreams, man is no longer a volitional being; his senses cease to perform their functions; identity is lost; he confounds time and space; the strangest persons and events cause no astonishment; his attention is almost suspended; his imagination is unbounded, his memory surprising. All these psychological states are found in the hallucinations of dreams, and establish their difference from waking hallucinations.

Voltaire dreamt the first canto of his Henriade differently from the plan which he had adopted in writing it. He was struck with the singularity: "In my dream," says he, "I said what I should hardly have said awake; I therefore thought and reflected involuntarily. I possessed no freedom of will, and yet I combined ideas with shrewdness, and even with genius."

The hallucinations of dreams are frequently exhibited in the intermediate state between sleeping and waking. M. Al. Maury gives them the name of hypnagogique (that which brings on, andsleep).* It is with some reason that Purkinge and Grutheisen called them the elements of dreams. Cerebral congestion appears favorable to their production; but the generalization of this fact would be contrary to experience, for thousands of persons dream without having hypnagogical hallucinations, headaches, or congestive symptoms.

The object which is perceived in a dream may be the faithful representation, or almost the identical object itself which is perceived in an hallucination, as the object of an hallucination may be the exact reproduction of the object of a dream.

Abercrombie, whose work on the Intellectual Faculties has acquired an extraordinary reputation in England, and justly merits a translation into our language, is of opinion that dreams and hallucinations are closely related to each other. In support of this doctrine, he quotes the following fact: "A distinguished physician, harassed with fatigue, and worn out with anxiety in consequence of the illness of one of his children, slept in his chair, where he dreamed that he saw a gigantic baboon. He awoke much agitated, arose and went towards a table that was in the middle of the room. He was perfectly awake, and recognized the objects around him. At the end of the room, against the wall, he distinctly saw the baboon making the same grimaces as in his dream. This apparition lasted for half a minute."*

* Ann. Med. Psych.; t ii. p. 26.

Sir Walter Scott says that the analogy between dreams and illusions is striking, as is shown in the following facts: "Thus, a dreamer hears a noise not sufficiently loud to awaken him entirely; at the same time something accidentally touches him. These impressions instantly form a part of his dreams, and adapt themselves to the tenor of the ideas that occupy his mind, whatever they may be. Nothing is more remarkable than the rapidity with which the imagination furnishes a complete explanation of this interruption to sleep, according to the manner in which ideas are presented by the dream, even without requiring a moment's respite for this operation. For example, if a duel is the subject of the dream, the noise that is really heard becomes the discharge of the pistols of the combatants. If an orator, in his dream, is making a speech, the noise becomes the plaudits of his supposed auditory. If the dreamer is transported in his dreams to the midst of ruins, the noise appears that of the fall of some portion of the walls.

"In a word, an explanatory system is adopted, in which the rapidity of thought is so great that, if we suppose the noise heard to be the first efforts of some one to awaken the sleeper, the explanation, although requiring a certain train of deductions, is usually finished and complete before a second effort has perfectly awakened the sleeper. There exists in the succession of ideas during sleep, an intuition so rapid that it recalls the vision in which the prophet Mohammed saw all the wonders of heaven and hell, although the water contained in the jar, which was upset when his ecstasy commenced, was not completely emptied when he recovered the use of his ordinary faculties."

Hallucinations in dreams are sometimes the result of association of ideas, or reminiscences. Amongst the curious cases of this nature, those that we are about to relate have great interest, and prove that dreams give rise to the most singular combinations, and the strangest facts.

* Abercrombie, Inquiries concerning the Intellectual Powers and the Investigation of Truth. London, 1841.