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constitutes a disorder of that kind of sensibility which has been designated by the term muscular sense.
Analogous phenomena are encountered in normal individuals; the sensation of heaviness or of lightness of the limbs, which we experience during sleep, are justly attributed by Beaunis1 to disturbances of the muscular sense; the illusions referred to an amputated limb are often accompanied by motor hallucinations.
Motor hallucinations are frequent among the insane. Some feel themselves being raised from their bed, being shaken continually against their will, etc. Others, like the medieval sorcerers, imagine themselves flying in the air.
By a well-known psychological process the sensation tends to transform itself into an act, the motor image into a movement. The motor hallucination becomes an impulse. The patient feels with astonishment that his limbs, his tongue, or his mouth become the seat of movements in which his will takes no part. A patient of Krishaber's, for instance, felt his legs "move as though endowed with a power other than that of his own will." Many of the persecuted or mystic patients affirm that they have been transformed into automatons, and that God or their enemies, as the case may be, make them go and act as they wish.
There is a certain form of motor hallucinations which deserves particular attention by reason of its frequency, its clinical importance, and its high psychological interest; these are the verbal motor hallucinations which have been admirably described by
1 Les sensations internes, 1889, Paris, F. Alcan.
Séglas.1 As their name indicates, they affect the function of speech. The patient is conscious of involuntary movements of his tongue and lips, identical with those which produce articulation of words. The sensation may exist alone or it may acquire such intensity that it is transformed into actual motion, and the patient begins to speak in spite of himself. Often the pathological movements are scarcely apparent, being limited to an inaudible whisper. Sometimes the impulse is so strong that it results in loud talking or screaming. The remarks made by the patient in such a case may be entirely discordant with his true sentiments. In this way such patients may unintentionally insult their relatives, making use of obscene language, blasphemies, etc. At other times the thoughts of the patient are spoken out in spite of himself. Pierracini has termed
this phenomenon "the escape of thought.' Séglas.)
Verbal motor hallucinations exercise upon the function of speech, even in those cases in which they do not reach the stage of actual articulatory movements, so powerful an inhibitory influence that the subject becomes totally unable to speak. This is in perfect accord with the observation of Stricker, who found that two verbal motor images cannot exist at the same time. Already occupied by the hallucinatory motor image, the consciousness remains closed to normal motor images. Verbal motor hallucinations are thus a cause of mutism. Graphic motor hallucinations affect written speech.
1 Leçons cliniques. Also Les troubles du langage chez les aliénés. (Bibliothèque Charcot-Debove.)
"The graphic image then comes into play, and in consequence of the morbid irritability of the special cortical centre for written speech the patient has the exact perception of a word with the aid of the representations of the co-ordinate movements which would accompany it if he were really writing the word.” 1
When this morbid irritation attains a certain degree of intensity the hallucination becomes a graphic impulse and gives rise to automatic writing, which is often met with in the "writing mediums."
The interpretation of motor hallucinations varies in different patients. Some complain that their enemies govern their tongues by means of invisible wires. Others, feeling themselves no longer masters of their own organs, are naturally led to think that a strange personality has become established alongside of themselves. Some of the "possessed" of the mediaval times undoubtedly had motor hallucinations.
Motor hallucinations generally involve a grave prognosis. They indicate an already advanced disaggregation of the personality. Therefore they are chiefly encountered in the chronic psychoses; they may appear, however, in certain acute psychoses, such as melancholia (Séglas) and alcoholic delusional insanity, (Vallon, Cololian).2
Theories of hallucinations. I shall but mention the so-called psychological theory, according to which hallucinations are supposed to be a phenomenon purely of ideation. Physicians and physiologists have long ago
1 Séglas. Les troubles du langage, p. 246.
2 Cololian. Les hallucinations psycho-motrices verbales dans l'alcoolisme. Arch. de Neurol., Nov. 1899.
abandoned this theory. But though all authors today admit the existence of a material pathological process as the foundation of hallucinations, they are far from being in accord as to its nature and as to its seat.
Jean Muller is of the opinion that hallucinations are the consequence of abnormal irritation of the peripheral sensory organ.
According to Meynert they result from the automatic activity of the subcortical cerebral centers, which are no longer inhibited by the cerebral cortex as they are in the normal state.
The primary cause of hallucinations would thus be a suppression of the inhibitory power of the cortex, which is one of the manifestations of cortical paralysis. The hallucination is then the consequence of a supremacy of the inferior cerebral functions over the higher ones.
Finally, according to Tambourini, whose opinion is to-day the most widely accepted one, hallucinations are produced by the automatic activity of a psychosensory projection-center.
Under what conditions does the automatism of the projection-center come into play? Is it under the influence of direct irritation resulting, for instance, from a tumor or from a circumscribed patch of meningitis localized exactly at this center? Such cases occur. Sérieux has observed verbal motor hallucinations in a general paretic in whose case the autopsy showed a predominance of the lesions of meningo-encephalitis at the level of the lower portion of the left third frontal
1 Sur un cas d'hallucination motrice verbale chez une paralytique générale. Bull. de la soc. de méd. ment. de Belgique, 1894.
convolution. The lesion must not, however, be a too destructive one. Indeed, for a center to be able to produce hallucinations, it is necessary that conditions of integrity be preserved sufficient to permit its activity' (Joffroy).1
Most frequently, however, the center of projection is not the seat of any demonstrable lesion. It seems, then, that in most cases the hallucinations are the consequence, not of a direct irritation of the psychosensory center itself, but rather of an indirect irritation coming from another portion of the cortex. This explains why hallucinations are always a secondary phenomenon, and why they are but an expression, a reflection of the pathological preoccupations of the patient.
Wernicke has conceived a very ingenious theory of hallucinations, founded upon his general hypothesis of sejunction. By this term he designates a temporary or permanent interruption of the paths followed normally by a nervous impulse. This impulse cannot pass on freely, and accumulates above the point of the lesion like the water in a river above a dam. When this accumulation occurs in a psychosensory projectioncenter it sets up there a state of abnormal irritation of which the clinical expression is a hallucination.
1 Les hallucinations unilatérales. Siebert has also reported a case in which very pronounced hallucinations of the sense of smell persisted for a long time and subsequently disappeared by degrees. At the autopsy the hippocampus was found to be destroyed by a tumor. The author supposes that the hallucinations were caused by irritation of the center in question by the growth, and that they did not cease until this center was destroyed. (Monatschr. für Psych. u. Neurol., Vol. VI.)