In treating the subject of dreams, one class of philosophers believe the mind to be under the influence of good and evil spirits, and that as one or the other of these invisible attendants gains ascendency, the person will experience happy or distressing dreams. Gall, in his reduction of the mind to its ultimate elements, has shown that these spirits are to be found in the animal' economy, and are the activity of the organs of the mind itself. "Almost all physiologists," he says, "agree, that, in dreaming, animal life is partially active. They are right, and yet they deny the plurality of organs! But dreams cannot be conceived without the hypothesis of this plurality.

"When in sleep particular organs of animal life become active, the sentiments and ideas which depend upon them most necessarily be awakened; but, in this case, the activity is independent of the will.

"When one organ only is active, the dream is simple : the object of our love is embraced, harmonious music is heard, we fight our enemies, accordingly as one organ or another is performing its functions."

The action of the organs of veneration and benevolence, combativeness and destructiveness, in combination with other fundamental elements of the mind, will account for many of the singular associations during sleep; and in the language of the fair Poetess will show, that

"It is Thought at work amidst buried hours, It is Love keeping vigil o'er perished flowers, Oh! we bear within us mysterious things, Of Memory and Anguish unfathomed springs, And Passion, those gulfs of the heart to fill, With bitter waves which it ne'er may still."

When the mental action is sufficiently intense in the dream, the faculty of speech is brought into play, and by an increased intensity, locomotion is added. This constitutes complex dreaming. Volition, the result of the activity of the intellectual organs; obeys those powers of the mind in operation, and therefore, when dialogue is the character of the dream, if the intellectual excitement is sufficiently intense, vocal action follows; and in like manner, when change of place is desired, volition plays the same part with the organs of locomotion - causing somnambulism.

Sleep-talking and sleep-walking occur in the stages of dreaming and torpor. When they occur in the former stage, the person retains the circumstances on awaking; but when in the latter, there is no remembrance of them. Volition is developed in proportion, and acts in obedience to the mental, organs in action; and memory is unfolded in a like ratio to the impressibility of the sensational apparatus.

An instance combining these phenomena was familiar to the author. The subject, a merchant's clerk, was of a sanguineo-nervous temperament - irritable and timid. It was a favorite amusement with his fellow-clerks, to commence a conversation with him (as soon as he was sufficiently asleep not to be easily aroused), relative to robbers breaking into the store-house. From his timorous disposition, this subject was undoubtedly on his mind when he retired to rest, and therefore could, by skilful management, readily be made the theme of his thoughts in sleep. By this management, he could be induced to converse, leave his bed, dress, go into the street and combat any person who should oppose him in the feigned character of a robber. On awaking he could relate nearly the whole transaction.

In this case the mental action was intense, and volition was perfect in a corresponding ratio. The auditory organs, which were the principal avenues to the mind, were but little impaired, and as he could be readily aroused by concussion, the sense of touch was also in a tolerable state of integrity. In most instances of this character, the senses are apparently obliterated ; the individual is not easily aroused, and memory seldom retains any of the circumstances.

Not long since, a person in the stage of torpor leaped from the second story window of a hotel in this city; alighting on the stone pavement, he considerably sprained his ankle. -After running about twenty rods he came in contact with a lamp-post to which he clung, and from which he was taken in a state of sound sleep, being unconscious of his situation. On awaking he had no remembrance of what had occurred. The injury, had it been transmitted to the brain, was sufficient to change the character of his thoughts, and to arouse him from sleep. This, however, did not occur till some time afterwards. Volition was as perfect in this case as in the former, but memory was not, volition depending upon the intensity of mental action, memory upon the integrity of the special senses.