INSANITY ( Lat. from insanits, insane, unsound. from in-, nut + satins, sane, sound; connected N‘illl adot, ann.e, crL:n. sound. safe), or 1.rx.“-v. A manifestation of disease of the brain characterized by a general or partial derangement, of one or more of the mental processes, in which, while is nut abolished, mental activity is weakened or perverted. This definition is modified from that given by Hammond. :Ind, like all attempted definitions of the term. is inadequate. Insanity is not mental disorder, althoimh disorder of mind is always present in insanity. A person mho mistakes red for gray has disordered men tality; but he is not insane. though color-blind. T)cfeetive reasoning, mhiell leads a loan. for in stance, into a toil investment, is it disordered mental process, yet not insanity. Thus it is matter of extreme Ilitlictilty to define insanity so as not to inelmle the condition: iu sleep, or trance. or the common manifestations of gen eral neuroses Iike epilepsy, hysteria. and chorea, the delirium of fever, aente intoNieations, etc. There is no rigid line of demareation between sanity and insanity. The conditions of each Lear close resemblance. The processes of mental action in sanity in insanity are of the same kind, although they differ in their origin and in the dogrel( of their intensity. It is often said that every one is more o less insane. This is an ab surdity. as insanity is a manifestation of disease, not merely a 11:11110 for mental disorder. The notion. also, that one may be insane on one subject. and otherwise perfeetly sane. is erro• for the same reason. .1,11 insane person may betray his mental condition when drawn out by one line of thought, or %ellen one topic is broached: hut, if insane. he is diseased and in no respect sane, even if able to carry on his business or perform complex acts properly.
To understand insanity one must understand the normal action of the mind and have some knowledge of the physical basis of mental action: that is, of the cerebral cortex and its association fibres, (See NERVOUS Sysrr:m.) The funetirms of the cerebral cortex are: (1) To receive iut pressions from the organs of sensation (conscious perceptions) ; (2) to group these impressions into a unit, known as a concept; (3) to store up these concepts. for future lecognition and revollection (memory), for gathering into innel combinations tintaginati,m), and for use as a basis of thought ; ( I) to express thought in speech and action; (5) to experience emotion %%Illicit accompanies mental activity: (6) to exert self-vontrol user all mental :minim (Starr.) This statement is true enough for the praetieal study of insanity, and is made to avoid opening the subject of the connection between nenous and mental phenomena. \1 hilt. many alienists accept the anatonM•al basis, and brliete ill It of the mental into the material, others claim that the activity of the highest nervous centres is attended by a mental state, but is not in itself it mental state. (Si• Alim).) At all events, %diet: areas of the vortex are diseased, 011c or more of the cortical functions named may he 1111•111:11 results. If changes in blood-simply or in nutrition occur, or disease affects the entire cortex, insanity maw result: and, as a lesult. thought becomes illogical, emotion becomes excessive, or arises without ex ternal stimulus. action is irregular or purpose less, and conduct is not properly adjusted to surrounding circumstances. In the insane person impressions from sense perceptions may be wrongly interpreted. An illusion is a falsely
interpreted sense perception. For example, a chair may be mistaken for an animal; the rumble of a wagon may be mistaken for the angry voices of a pursuing mob. Ideas may arise Ivitlimit any sense perception. When quiet exists, the. insane parson may hear voices; he may see faces in all empty space; he may smell burning flesh \\ /It'll 110 odor is present. These false perceptions without external origin in sensiiry experiences are called hallucinations. A mistaken idea may be harbored by any one: for example. one may believe that a stone is numb larger than it is. Nleasureinent and examination ronvince him of his error. and. if he is sane, he corrects his judg ment. The insane luau is not affected by logical methods. and retains his erroneous idea in spite of demonstration and reasoning. A mistaken idea accepted without logical foundation is a delusion; it retained in spite of demonstration of its falsity, it is :in insane delusion. people frequently, though out necessarily, ex hibit delusions, varying according to the bodily ills. the occupation or profession. the emotions experienced, or their surroundings. t'ert a in forms of delusion are fairly constant in certain types of insanity. For example. in melancholia patients often declare that they have committed some great sin: in paranoia. delusions of per sueution and of conspiravy are present ; in mania. delusions of identity. or of being an important person. are frequent; in :ileoliolie insanity, thc delusion of marital infidelity is common; in gen eral paresis, a number of grandiose delusions--(If power. of wealth. of strength, of beauty—are present in one stage: and in early stages of dementia delusions of grandeur are also noticed. less frequency. Ilisturbances of emotional feeling occur in insane people: depression, ex altation. Lang-nor, and absurd joy are noticed in dill'erent ease. Acting under the impulse of delusion or hallueination the insane exhibit dis. lurbancc in voluntary action and conduct. In sufficient motive causes action, because of im paired intellectual power, or impaired memory, or sub-consciousness. Consciou.sacss is impaired; external objects are often ignored; changes of personality occur.
Besides these mental signs of insanity, there are many somatic. or physical, symptoms. These are generally divided into five classes: (1) Sen sory symptoms, such as pain, hyperlesthesia (q.v.), or amestbesia (q.v.). (2) Changes in reflex action, front disease or other cause, such as lessened knee-jerk (q.v.) or dilated pupils. (3) Motor disturbances, such as loss of muscular control, shown in altered handwriting, altered speech, gait, attitude, etc. ; convulsions or paralysis may also occur. (4) Changes in cir culation and nutrition, such as pallor or flush ing, loss of flesh, impaired digestion. (5) Dis turbances of sleep, which occur commonly.
The study of disease affecting the mind is called alienism, or psychiatry, less often (in Great Britain) medico-psychology. The spe cialists who give their attention to insanity and the treatment of the insane are called alienists.
An accurate classification of diseases affecting the mind is difficult. Various alicnists have pro duced different tables, but the most satisfactory is the classification of KratIt-Ebi»g (q.v.), or some modification of it, such as the following table, as adopted in his lectures by ..11. Allen Starr (q.v.), of New York: