HALLIICINA'TIONS are morbid conditions of mind in which perception takes place where no impression has been made upon the external organs of the special senses, and where the object is believed to be real and existing. A picture is presented to the imagination when no ray of light has fallen upon the eye; a voice is heard when all around is silent; a pleasant smell fills the nostril when neither flowers nor feast give forth their fragrance. Delusions, on the other hand, originate at the other extremity of the chain of consciousness in the mind itself, and consist in erroneous interpretations of real sensations. A form passes across the vision, and it is regarded as a phantom, or a demon, or what is not and cannot be; a voice may address the listener in accents of tenderness and friendship, which before they reach the mind have assumed the shape of insults and calumnies; and the fresh odor of a rose may suggest notions of poison and pollution. But hallucinations may involve internal experiences as well as the reports from the outer world; nor .is it invariably possible or necessary to distinguish hallucinations from delusions. There is a composite state in which the external impres sion is and the interpretation from such an impression, had it been real, is trroneous. A clock is heard by a patient to strike where not a sound is audible by others, and the chime is held to be the announcement of the crack of doom. In all these cases, the sensoritun itself must be held to be at fault, whether the nerves of seeing, hearing, etc., be structurally affected or not. These phenomena are observed in connec tion with all the senses, hut in different proportions; the frequency being perhaps in relation to the number of healthy sensations of which the organ is the natin•al channel, and to the degree of excitement and cultivation to which it is ordinarily subjected. According to one authority, hallucinations of hearing constitute two-thirds of the whole observed; but, upon a more careful analysis, the following tabular expression of fre quency appears to be correct: hallucinations of hearing, 49; of vision. 48; of taste, 8; of touch, 3; of smell, I. These conditions are detectable in all mental diseases; but the proportion varies according to the form and the intensity of the alienation. All are more frequent in mania than in monomania and fatuity; and errors of vision are more numerous than those of hearing in mania. Lord Brougham at one time held that the presence of hallucinations should be elected into a crucial test of the existence of insan ity. Practical men, however, demonstrate that derangement is not necessarily conjoined with such a symptom. Esquirol held that of 100 lunatics, four-fifths would be affected
with hallucinations. Of 145 individuals in Bicetre, Baudry found that 56 presented hallucinations; and the subsequent researches of 'Dore and Aubanel tmthe same hos dital showed 122 affected out of 443 Maniacs, monomaniacs, etc. Bras:re de Boismont, Des Hallucinations (Paris, 1845); Aubanel and 'More, Rechsrelles Statistiques faites u l'llospice de Dicare; Michea Die Delire des Sensations (Paris, 1848).
Hallucinations of Sane a great majority of eases, hallucinations can readily be traced to mental alienation, which is cognizable by other signs, or to conditions of the nervous system, which impair or pervert without overthrowing the mind; or to general constitutional states, or positive diseases, such as in the case of Nicolai, which involve disturbance of the functions of the external senses. There is, however, a class of phenomena which cannot be included under any of these categories; where objects appear; voices tempt, threaten, soothe, or where a series of impressions are received by the mind, without any corresponding sensation; where the system is perfectly healthy, and where the individual affected is conscious that what he sees or hears is unreal. Medical experience, however, goes to show that under such circumstances the nerve, or some organ connected with the development of special sensation, or the brain itself, is in an abnormal or excited condition, which falls short of disease, not interfering with the regular discharge of the ordinary functions of these parts of the economy, and not being detectable in any other way, and which is sometimes compatible with great intel ligence, and even genius. As illustrative of the latter proposition. and of the least mor bid aspect of such phantasmata, it may be mentioned that the late earl Grey was haunted by a gory head, which he could exercise at will. Swedenborg, while at the head of the government, saw members of the heavenly hierarchy seated among the ministers at the council board, and bowed reverentially to them. Bernadotte encountered a woman in a red cloak in his rides; and a patient has been described who was followed first by a cat, then by a tatterdemalion beggar, and then by a skeleton which never left him. walked side by side, joined his family circle, and peered through his curtains at night. Yet Swedenborg knew that it was not flesh and blood realities he acknowledged; the king shrunk from, but repudiated the red cloak; and the patient disbelieved the skeleton, and detected its true nature and origin.