A motor hallucination may be defined as an imaginary perception of a movement. It constitutes a disorder of that kind of sensibility which has been designated by the term muscular sense.

Analogous phenomena are encountered in normal persons, the sensation of heaviness or of lightness of the limbs, which we experience during sleep, are justly attributed by Beaunis! to disturbances of the muscular sense; the illusions referred to an amputated limb are often accompanied by motor hallucinations.

Motor hallucinations are frequent in psyehotics. Some feel themselves being raised from their bed, shaken continually against their will, etc. Others, like mediaeval sorcerers, imagine themselves flying through 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 impidse. The patient feels with astonishment that his limbs, his tongue, or his mouth become the seat of movement 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 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 Seglas.2 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." (Quoted by Seglas.)

1 Les sensations internes, 1889, Paris, F. Alcan.

2 Legons cliniques. Also Les troubles du langage chez les alienis. (Bibliotheque Charcot-Debove.)

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 Strieker, who found that two verbal motor images cannot exist at the same time. Already occupied by the hallucinatory motor image, consciousness remains closed to normal motor images. Verbal motor hallucinations are thus a cause of mutism.

Graphic motor hallucinations affect written speech. "The graphic image then comes into play, and in consequence of the morbid irritability of the special cortical center for written speech the patient has the exact perception of a word with the aid of the representations of the coordinate 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 "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 beside them. Some of the "possessed " of mediaeval times undoubtedly had motor hallucinations.

Motor hallucinations generally imply a grave prognosis. They indicate an already advanced disaggregation of the personality. Accordingly they are chiefly encountered in the chromic psychoses; they may appear, however, in certain acute psychoses, such as melancholia (Seglas) and alcoholic delusional states (Vallon, Cololian).1

1 Seglas. Les troubles du langage, p. 246.