686 STRUCTURE OF THE CEREBRUM. 



impressions, indeed, influence the whole metabolism. Strurapell describes the case of a boy 

 wh^nsory inlets were all paralysed except one eye and one ear, and when these inlets were 

 do^ The boy fell asleep, showing how intimately the waking condition is bound up with 

 sensory afferent impulses reaching the cerebral centres.] 



Xpnotics, such as opium, morphia, KBr, chloral, are drugs which induce sleep.] 



Hypnotism or Animal Magnetism. -[Most important observations on this subject were made 

 bf Braid of Manchester, whose results are confirmed by many of the recent re-discoveries of 

 Weinhold, Heidenhain, and others.] Heidenhain assumes that the cause of this condition is 

 due to an inhibition of the ganglionic cells of the cerebrum, produced by continuous feeble 

 stimulation of the face (slightly stroking the skin or electrical applications), or of the optic 

 nerve (as by gazing steadily at a small brilliant object), or of the auditory nerve (by uniform 

 sounds) ; while sudden and strong stimulation of the same nerves, especially blowing upon the 

 face abolishes the condition. Berger attributes great importance [as did Carpenter and Braid 

 lone ago] to the psychological factor, whereby the attention was directed to a particular part of 

 the body. The facility with which different persons become hypnotic vanes very greatly. 

 When the hypnotic condition has been produced a number of times, its subsequent occurrence 

 is facilitated, e.g., by merely pressing upon the brow, by placing the body passively in a certain 

 position, or by stroking the skin. In some people the mere idea of the condition suffices. A 

 hypnotised person is no longer able to open his eyelids when they are pressed together. Ihis 

 is followed bv spasm of the apparatus for accommodation in the eye, the range of accommodation 

 is diminished, and there may be deviation of the position of the eyeballs ; then follow phenomena 

 of stimulation of the sympathetic in the oblongata ; dilatation of the fissure of the eyelids and 

 the pupil, exophthalmos, and increase of the respiration and pulse. At a certain stage, there 

 may be a great increase in the sensitiveness of the functions of the sense-organs, and also of the 

 muscular sensibility. Afterwards there may be analgesia of the part stroked, and loss of taste ; 

 the sense of temperature is lost less readily, and still later that of sight, of smell, and of hearing. 

 Owing to the abolition or suspension of consciousness, stimuli applied to the sense-organs do 

 not produce conscious impressions or perceptions. But stimuli applied to the sense-organs of a 

 hypnotised person cause movements, which, however, are unconscious, although they simulate 

 voluntary acts. In persons with greatly increased reflex excitability, voluntary movements 

 may exefte reflex spasms ; the person niav be unable to co-ordinate his organs for speech. 



Types. According to Griitzner, there are several forms of hypnotism : (1) Passive sleep, 

 where words are still understood, which occurs especially in girls ; (2) owing to the increased 

 reflex excitability of the striped muscles, certain groups of muscles may be contracted a condi- 

 tion which may last for days, especially in strong people ; at the same time ataxia may occur, 

 and the muscles may fail to perform their functions (artificial katalepsy). During the stage of 

 lethargy in hysterical persons, the tendon reflexes are often absent (Charcot and Richer); (3) 

 autonomy at call, i.e., the hypnotised person in most cases the consciousness is still retained 

 obeys a command, in his condition of light sleep. When the hand is grasped or the head stroked, 

 he executes involuntary movements runs about, dances, rides on a stool, and the like ; (4) 

 hallucinations occur only in some individuals when they waken from a deep sleep, the hallucina- 

 tions (usually consisting of the sensation of sparks of fire or odours) being very strong and well- 

 pronounced; (5) imitation is rare, ordinary movements, such as walking, are easily imitated, 

 the finer movements occur rarely. The "echo-speech" is produced by pressure upon the neck, 

 speaking into the throat, or against the abdomen. Pressure over the right eyebrow often ushers 

 in the speech. Colour-sensation is suspended by placing the warm hand on the eye, or by 

 stroking the opposite side of the head (Cohn). Stroking the limbs in the reverse direction 

 gradually removes the rigidity of the limbs and causes the person to waken. Blowing on a part 

 does so at once. Insane persons can be hypnotised. Disagreeable results follow only when the 

 condition is induced too often and too continuously. 



Hypnotism in Animals. A hen remains in a fixed position when an object is suddenly placed 

 before its eyes, or when a straw is placed over its beak, or when the head of the animal is pressed 

 on the ground and a chalk line made before its beak (Kircher's experimentum mirabile, 1644). 

 [Langley has hypnotised a crocodile.] Birds, rabbits, and frogs remain passive for a time after 

 they nave been gently stroked on the back. Crayfish stand on their head and claws (Czcrmak). 



375. STRUCTURE OF THE CEREBRUM MOTOR CORTICAL CENTRES. [Cerebral Con- 

 volution. A vertical section of a cerebral convolution consists of a thin layer of grey matter 

 externally enclosing a white core (fig. 478). The cortex consists of cells and fibres embedded 

 in a matrix, and to the nerve-cells nerve-fibres proceed from the white matter. The nerve-cells 

 of the cortex vary in size, form, and distribution in the different layers and also in different 

 convolutions. Taking such a convolution as the ascending frontal or motor-area type, we get 

 the appearances shown in fig. 474. It is covered on its surface by the pia mater. (1) The 

 most superficial layer is narrow, and consists of much neuroglia, a network of branched nerve- 

 fibrils, a few scattered small multipolar nerve-cells, and a layer of very small medullated nerve- 

 fibres ; (2) a layer of close-set small, angular, or short pyramidal nerve-cells ; (3) the thickest 

 layer or formation of the cornu ammonis, consisting of many layers of larger pyramidal cells, 



