Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/297

Rh ANIMAL MAGNETISM.] MAGNETISM 279 successful, as the operator would readily comply with all the conditions ; but most of these phenomena can be explained physiologically, and those which cannot be so accounted for will remain- hidden until we get further light on the physiology of the nervous system. The symptoms of the hypnotic state, as shown by Heidenhain, may be grouped under four heads : (1) those referable to conditions of the seusorium or portion of the brain which receives nervous impulses, resulting in move ments of a reflex and imitative character ; (2) insensibility to pain, and various forms of perverted sensation; (3) increased irritability of the portion of the nervous system devoted to reflex actions; and (4) states of the nervous centres controlling the movements of the eye, the accom modation of the eye to objects at various distances, and the movements of respiration, &c. 1. The State of the Sensorium. By the sensorium is meant that portion of the nervous system which receives impulses from the nerves coming from the organs of sense, such as those from the eye, ear, nose, tongue, and skin. Each of these nerves brings its message to a portion of the central nervous system in intimate connexion with the rest of the nervous system. This message may possibly arouse nervous actions associated with consciousness, or it may not ; or the nervous actions of consciousness may be so transient as to leave a faint impress on the memory, so that it can be revived only if no great interval has elapsed since the impression was made on the sense organ. If, however, the impression be vivid, then it may be revived long afterwards. This impression may be consciously perceived, and then any apparent effect may end ; but it may set up a set of actions, resulting in motion, which are apparently of a reflex character. Thus, suppose a person in the dark ; light is suddenly brought before the eye ; this affects the retina, and through the changes in it the optic nerve and central organ ; there may be consciousness or there may not ; if the person be wide awake he will see the light ; if he be asleep he will not see it, at all events he will give no indication of seeing it ; on awaking, he may have a recollection of a dream in which light has a place, or his memory may be blank ; but nevertheless the light will cause the pupil of the eye to contract by reflex action without his consciousness ; and perhaps, also, without consciousness, the sleeping person may make an effort to avoid the light, as has been noticed in the case of somnambulists. Now, when a patient has been thrown into a weak hypnotic state, there may be a vivid recollection on awaking of all that happened during the apparent sleep. This implies, of course, that conscious sensory perceptions took place during the condition. Memory depends on the direction of the attention to sensations. If the effort of attention be strong, the recollection will probably be vivid, and the converse is true. But this does not preclude the supposition that sensory perceptions may come and go, like the shadows of clouds on a landscape, without any attempts at fixing them, and consequently with no recollection following their occurrence. The sensory perceptions may have existed for so short a time as to leave no impress behind. This may explain how it is that in the deeper forms of hypnotism there is either no recollection of what occurred or the recollection can only be aroused by hints and leading questions. Attention is necessary, therefore, to form a conscious idea arising out of a sensation. It is generally admitted by physiologists that the cerebral hemispheres are the seat of the higher mental operations, such as attention, &c., although the interdepend ence of these hemispheres with the lower sensory ganglia, which receive all sensory impressions in the first instance, and with motor ganglia, which are, in like manner, the starting-points of motor impulses, is not understood. The one portion of the nervous system may work without the other. Thus, during free cerebral activity we pay little attention to what we see or hear, and consequently we remember nothing. A man in a reverie may have many impressions of sight or of hearing of which he has been really unconscious. On the other hand, the cerebral apparatus may be so attuned with the recipient portion that if the latter receives a message the former sympa thetically responds. For example, a mother sound asleep is disturbed by the slightest cry of her child, although loud sounds of other kinds may not awake her. It would appear then that impressions on the senses and the consciousness of impressions are two separate states which may occur in a manner independently ; that is to say, there may be purely sensory operations, in which conscious ness is not involved, or there may be the conscious repetition of old impressions, or what is called memory. Now it is a law of nervous action that processes which at first are always of a conscious kind may by repetition become so habitual as to be performed without consciousness. Thus a child learns to perform a piece of music on the pianoforte by conscious efforts, often of a painful kind ; each note has to be recognized, and the appropriate muscular movements required for its production on the instrument executed with precision and delicacy ; but by and by the music may be performed accurately even while the attention is directed to something else. In like manner, all movements which are the results of sensory impressions may become unconscious movements ; the sensory impressions are at first paid attention to ; but as they become habitual the mind becomes less and less engaged in the process, until the movements resulting from them are practically unconscious. A familiar illustration is that of a man in deep reverie walking along a street. Immersed in thought, he pays little or no attention to passers by ; as his eyes are open, their images, or those of adjacent objects, must affect his visual apparatus, but they arouse no conscious impression, and still those impressions, evanescent as they are, are sufficient to excite the appropriate movements of locomotion. These movements are in all respects like voluntary movements, but they are not really voluntary, showing that, by the machinery of the nervous system, movements like voluntary movements may be executed without volition. It is important to observe, however, that these movements are the result of sensory impressions. A man in the deepest reverie, with Lis eyes blindfolded, could not execute the requisite movements ; and when we see the blind walking in the streets, they afford no contradiction to this view, as their minds are busily engaged in noticing another set of sensory impressions derived from the sense of touch, muscular movement, and hearing, a set of impressions of the greatest importance to them, although of little importance comparatively to ordinary people, who are guided chiefly by visual impressions. A person in a state of hypnotism may be regarded as in a condition in which the part of the nervous apparatus associated with conscious perception is thrown out of gear, without preventing the kind of movements which would result were it really in action. Impres sions are made on the sensory organs ; the sensory nerves convey the impression to a part of the brain ; in the deepest condition of hypnotism these impressions may not arouse any consciousness, but the result maybe the ^ kind of movement which would naturally follow supposing the person had been conscious. The movements made by the hypnotic are chiefly those of an imitative kind. It has often been noticed that the mere suggestion of the move ment may not be enough to excite it ; to secure success,