Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/298

Rh 280 MAGNETISM [ANIMAL MAGNETISM. the movement must be made before the eyes of the person. For example, it is a common part of the exhibition of such persons for the operator to clench his fist ; the patient at once clenches his ; the operator blows his nose ; the patient does likewise ; but if the operator performs these actions behind the back of his patient the chances are that the patient will not repeat the movements. The condition seems to be one in which the sensory impression leads to no conscious perception and to no voluntary movement, but is quite sufficient to arouse those nervous and muscular mechanisms which lead to uncon scious imitation. The patient is in a sense an automaton played upon by the operator through the medium of the patient s sensory organs. It is important to observe that in deep hypnotism the patient has no idea corresponding to the movements he makes in obedience to the example of the operator. For example, suppose he is swallowing a glass of water and the operator tells him it is castor oil, at the same time making the requisite grimaces, the patient will imitate these grimaces without having any idea either of water or of castor oil. The grimaces are purely imitative, without any connexion with the idea which would naturally excite them. This is the case only with those deeply hypnotized. In some cases, however, the hypnotism is so deep as to resemble coma, and in these there is no trace of any sensory impressions or of move ments. In cases where the hypnotism is slight, there may be a curious mixture of effects. Here the patient may be partially conscious of the requests made to him, and of the imitative movements executed before his eyes ; to some extent he may resist the commands of the operator, he may feel he is being fooled, and yet he may perform many ridiculous actions ; and when he awakes he may have a vivid recollection of the events in which he participated. A hypnotized person, in fact, is in a state similar to that of the somnambulist, who acts the movements of a dis turbed dream. There are many degrees of the sleeping state, from the profound condition resembling coma to that of the light sleeper who starts with every sound. In some sleeps there are dreams in which the sleeper is so occupied with the phantoms of thought as to pay no attention to external impressions, unless these be sufficiently powerful to awake him, whilst there are other sleeps in which the boundary between the conscious reception of new impres sions and the reproduction of old ones is so thin as to permit of a blending of the two. In this kind of sleep, a epoken word, a familiar touch, the suggestion of something in keeping with the thoughts of the dreamer, are sufficient to change the current of the dream, and even to excite movements. When the ideas of the dreamer cause movements corresponding to these ideas, then the dreamer becomes a somnambulist. He acts the dream ; according to the depth of the semi-conscious state will be his capacity for responding to external impressions. Some somnambu lists respond to external suggestions readily, others do not ; and in all there is almost invariably no recollection of the state. Artificial hypnotism is a condition of the same kind, though usually not so profound. The question now arises as to how this artificial state may be induced. In one awake and active, all sensory impressions as a rule are quick, evanescent, and constantly renewed. New successions of images and thoughts pass rapidly before the mind during walking, working, eating, or in the leisure hours of social life ; but none last so long as to cause fatigue of any particular part of the body. By and by there is a general feeling of fatigue, and then sleep is needed to restore exhausted nature. But if the attention be fixed on one set of sensory impressions, fatigue is much sooner experienced than if the impressions are various in kind and degree. Thus one or two hours spent at a picture gallery or at a concert, if the attention be devoted to the impressions on the eye or ear, usually cause fatigue. It would appear that the method of exciting hypnotism by causing the patient to gaze at a bit of glass or a bright button depends in the first place on the feeling of fatigue induced. At first there is a dazzling feeling ; then the eyes become moist ; images become blurred and indistinct, and seem to swim in the field of vision ; the field of vision becomes unsteady, and just about this period ideas do not pass in the mind in orderly sequence, but irregularly, as in the few minutes immediately before passing into sleep. At this stage also the pupils become widely dilated, and the eyeballs become more prominent than usual. The innervation of the iris must be understood, so as to appreciate the physiological meaning of these changes. The muscular structure of the iris is supplied by two nerves, the third cranial nerve and the sympathetic nerve. If the third nerve be cut the pupil dilates ; if the distal end of the nerve be irritated the pupil contracts. On the other hand, if the sympathetic nerve be cut the pupil contracts, whilst if the distal end be irritated the pupil dilates. These experimental facts show that the radiating fibres of the iris which dilate the pupil are under the control of the sympathetic nerve, whilst the circular fibres which contract the pupil are supplied by the third. Further it can be shown that the corpora quadrigemina, two ganglionic masses in the brain, are the reflex centres for the regulation of these movements. The optic nerve from the retina supplies the sensory stimulus which causes the pupil to contract. Thus, suppose light to be brought before the eye while the pupil is dilated ; the retina is affected, a stimulus is sent to the corpora quadrigemina along the fibres of the optic nerve, and from the corpora quadrigemina a nervous influence passes along the fibres of the third nerve to the circular fibres of the iris, causing the pupil to contract. It is also very probable that the corpora quadrigemina act as reflex centres for nervous impulses regulating the calibre of the blood-vessels of the eye, the vaso-motor nerves. If we apply these facts to the case of a hypnotized person, we find that (1) the pupil of a hypnotized person contracts energetically when light falls upon the eye, showing that the reflex mechanism is still intact; (2) just before the hypnotic state is induced the pupil dilates, indicating feeble nervous impulses passing along the third from the corpora quadrigemina; (3) at first, the eyeballs seem to sink in, but when hypnotism is complete they project in a manner similar to what has been observed in an animal when the arteries supplying the head have been compressed so as to make the brain anaemic or bloodless; and (4) the ophthalmoscope has not shown any change in the calibre of the blood-vessels of the retina in the hypnotic state. From a consideration of these facts and inferences Heidenhain was at first inclined to believe that hypnotism might be due to a reflex influence on the vessels of the brain, causing them to contract so as to permit the passage of only a small quantity of blood, and make the brain anaemic. This view, however, had to be abandoned, as the faces of hypnotized persons are usually red, and not pale, as they would be were the arterioles contracted. Further, Heiden hain performed a crucial experiment by giving to his brother nitrite of amyl, which causes dilatation of the vessels by vaso-motor paralysis, when he still found hypnotism could be readily induced, showing that the state was not caused by deficient blood supply. Heidenhain has advanced another and more probable hypothesis. During the past twenty years a new mode of uervous action, known as inhibitory action, has been discovered by physiologists. A good example is supplied by the innervation of the heart. This organ has nervous