As there are states of mind of a tonic character, such as hope, cheerfulness, etc., and others powerfully stimulant, as anger; so are there feelings of a depressing tendency, of which advantage may sometimes be taken to allay morbid excitement, and which, in the hands of a judicious practitioner, may be made to answer an excellent purpose, especially in nervous affections. Apprehension, fear, despondency, grief, and similar modifications of feeling, have a sedative effect both on the nervous and circulatory systems, which, though not very obvious when the cause is but slight and temporary, may under opposite circumstances become alarming, and, by a long continuance, has not unfrequently proved fatal. it is impossible, however, to give precise rules, for the remedial management of such influences. This must be left to the judgment of the practitioner, under the guidance of his general therapeutic principles, when the opportunity for their useful employment may offer. it is in disorders of pure nervous irritation that they are most efficient. Hysterical excitement will often yield to a depressing emotion as to a charm; and the violence of insanity will sometimes give way under the same influence.

* in a communication made by M. Jacobowitcb to the French Academy, upon the histology of the nervous system, it is incidentally stated that, whenever he had examined the brain and spinal marrow of animals which he had destroyed by the sedative poisons, as hydrocyanic acid, nicotia, conia, etc., he had found the structure of the cerebral and spinal nervous matter useless for histological examination, as the nervous and cellular elements were entirely destroyed, owing, as he supposed, to an interruption of their nutrition through the agency of the poison. (Arch. Gén., 5e sér., x. 499.)

Monotony of thought, emotion, or sensation has a singularly soothing effect on nervous excitement, and in health operates strongly in depressing the nervous functions of animal life. its effect, in producing drowsiness, which is a suspension more or less complete of these functions, is well known. Nor is the explanation of its depressing influence difficult. The cerebral centres of thought, volition, emotion, and sensation, like all other living parts of the system, are kept in action by their appropriate excitants, internal or external, deprived of which they cease to act. The centres of themselves are probably powerless. in the ordinary course of life, the agencies which keep them in operation are generally present, during the waking period, and sustain a regular degree of activity. But, if the attention can be turned strongly into one particular direction, so as to abstract from the cerebral centres the mental influences which constitute their proper stimuli, while the object of attention has itself so little interest as not to bring thought or feeling into play, the consequence is that the centres in general fall into a state of repose, while that corresponding to the object of attention, fatigued by its over-exertion, itself sinks into the same condition; and a universal depression of the functions of relation is induced. The person thus operated on becomes at first listless or languid, then drowsy, and at length sleeps more or less profoundly. This occupancy of the attention by one object, or a series of objects of the same nature, is what is here meant by monotony. To count one hundred or one thousand backward; to repeat mentally the multiplication table in a similar direction; to think over a series of sovereigns, or of historical events chronologically, in an ascending or descending scale; to keep constantly present to the mind the most uninteresting event of the day, or the dullest character of one's acquaintance; to listen to a prosy speaker, or to read resolutely a no less prosy book; these, or similar expedients, are often sufficient, not only to induce sleep under ordinary circumstances, but often to overcome very obstinate fits of wakefulness.

The same effect is produced by a similar monotony of impression on the senses. in reference to hearing, how often do we see drowsiness induced by simple and constantly repeated melody, as the lullaby of the mother; by the ceaseless roar of the waves upon a beach, of a waterfall, or of a breeze in the pine tops; by the buzz of insects, or the hum of machinery ! Through the sight, similar effects are produced by an intent gaze upon a single object, or upon a uniform succession of movement, as the waving of a field of grain, or the manual passes of a mes-merizer, the majestic rolling of the ocean, or the rocking of a cradle. But perhaps the strongest effects of this kind are produced through the sense of touch. A gentle movement of the fingers of another person through the hair, the slight touches of a skilful barber in shaving, the sensation of rocking motion, or the gentle friction of a soft hand upon the surface of the body, often have a wonderfully composing effect. I have not unfrequently seen the restlessness and intolerable uneasiness of nervous debility, or febrile disease, yield entirely to a continuous and quiet movement of the hand of the nurse over the extremities; and a similar friction along the back will often relieve for a time the most violent spinal neuralgia.

The cessation or diminution of habitual impressions upon the senses has a similar sedative influence. Thus, the exchange of the glare and glitter of a town, its unceasing rattle, and clatter, and bustle, for the soft green, and comparative stillness of the country, often produces the most happy effects in calming nervous agitation, and is among our most effectual remedies for purely nervous disorder induced by the artificial life of cities.

Artificial Somnambulism. Hypnotism. The powers of the so-called animal magnetism or mesmerism, which is nothing more nor less than a condition of artificial somnambulism, cannot be passed over without notice, in a list of sedative mental influences. That there is a peculiar condition of system induced under the operations of the animal mag-netizers, or practical biologists, or by whatever other name they may prefer to be called, I do not think that any one who has carefully and practically examined into the subject can deny. The state is not sleep, though analogous to it. The mental faculties, and emotional functions, and to a considerable degree the sensations, are in a state, as it were, of abeyance. They exist, but are not capable of original and voluntary exercise. The ordinary exterior influences have little or no effect. The internal impulses and motives which usually direct the mental operations have lost their power. The system is a sort of animated machine, which acts through an impulse given it before entering into the condition, or under suggestions made while in it, and continues to act in the direction of these influences without any self-controlling power. A singular attendant upon it is frequently an absence of sensibility to painful impressions, so that severe surgical operations may be performed without the least apparent suffering to the patient, and often without any recollection of them upon restoration of the ordinary state of the system. The anaesthesia is often as perfect as that induced by chloroform or ether; and it is said, though I have myself seen no case of the kind, that, as in etherization, the insensibility to pain is sometimes established before consciousness is lost. The special senses, on the contrary, though, like the mental faculties and the emotions, not in full exercise, are, like them, susceptible of impressions in accordance with the original direction taken by the mind upon entering the new state, or with suggestions afterwards presented to it from outward sources. The muscular action is under the same influence. It is often exercised in the direction of the original ruling impulse, or in that subsequently given; but otherwise is powerless. Thus, if a limb is moved into any position, it will often retain that position, as in cataleptic persons. indeed, I do not know how better to express the whole sensorial condition than to say, that it is in a sort of mental catalepsy, moving only as directed by some force exterior to itself. it is not, however, my intention to enter into a thorough consideration of this condition; but merely to treat of it as a therapeutic instrument, the proper application of which requires that it should be in some degree understood.