Idiocy is defined by Ireland as 'mental deficiency or extreme stupidity depending upon malnutrition or disease of the brain occurring either before birth or before the evolution of the mental faculties in childhood; while Imbecility is generally used to denote a less decided degree of such mental incapacity.' The difference between both conditions and dementia (see INSANITY) is that the dement was once sane and responsible, the idiot and the imbecile never developed mental capacity at all; they remained arrested children. The name amencia has been given to idiocy. The mental faculties never showed themselves in any high degree, because the organ of mind in the brain never developed. There are great varieties of idiocy and imbecility. Some of the lowest have no speech, no power of distinguishing between one person and another, no affection or hatred, no feelings of pleasure or pain, no power to take care of themselves, and can never be taught any of these things. In body such idiots are dwarfish, misshapen, ugly, with the features and expression of face often of the lowest of the lower animals, with no power of walking. This being the condition of the lowest varieties, they rise gradually in the scale till many imbeciles are beautiful in features, and reach normal bodily development, but are slightly wanting in some essential mental faculty, in intelligence, or in affection, or control, or self-guidance. The mental deficiency is in by far the majority of idiots and imbeciles accompanied by corresponding bodily weaknesses of some sort.
Idiots and imbeciles differ much in their capacity for further development under even favourable circumstances. Some can be greatly elevated towards the standard of average humanity, and can even be rendered fit to earn their own livelihood in simple trades or manual labour, while others cannot be in any way improved. They are especially subject to certain bodily diseases of degeneration, such as scrofula, consumption, rickets, and diseases of deficient nutrition generally. Two-thirds of idiots die of consumption. The great aims in treatment are to improve the bodily nutrition, the nervous and muscular action, and the habits, to teach co-ordinated movements and simple employments, such as gardening, mat-making, carpentering, &c., and to evolve the possible intelligence by an education through the senses. Some of them have one faculty or capacity fairly or even extraordinarily developed, while the general mental power is weak. Some are good musicians. Some can calculate well, while others are ingenious in constructiveness. Such faculties have in those cases to be especially cultivated. For this purpose good food, exercise, drill, warmth, fresh air, and music are necessary, and a careful study and testing of each case to find out its strong and weak points; and teachers who devote themselves to this particular kind of educative process are required. For most of them this can only be done in Training Schools for Idiots and Imbeciles, of which there are about twelve fully equipped in the United Kingdom. It is felt by many persons that in addition to these a kind of school is needed between them and the ordinary school, for the purpose of developing 'backward children,' of whom there are a considerable proportion in our schools—a deadweight on our teachers and on the progress of the ordinary scholars. Education should be suited to the educability and the inherent brain-capacity of the scholar. Congenital idiots and imbeciles may have attacks of acute insanity, for which they may need to be sent to asylums for the insane; but as a general rule such institutions are not suitable for them. Few benefactors of their kind deserve more honour than the pioneers in the right treatment and education of idiots and cretins, such as Read, Howe, Seguin, and Guggenbühl. Few things must have looked so disheartening, unattractive, and unpromising of good results. But from a scientific point of view, both psychologically and physiologically, the undeveloped minds and bodies of this class have great interest and high importance.
Ireland classifies idiocy into ten divisions: (1) Genetous, (2) Microcephalic, (3) Eclampsic, (4) Epileptic, (5) Hydrocephalic, (6) Paralytic, (7) Cretinic, (8) Traumatic, (9) Inflammatory, and (10) by deprivation of the senses. From this it is seen that there are many pathological causes of the disease. It is a popular error to suppose that all idiots have small heads. Three-fifths of them have larger heads than average men, and only a few (the microcephalic) are small-headed. It is quality more than quantity of brain that counts for mind. Cretinism is a very interesting variety of idiocy and imbecility, and is the subject of a separate article. The general causes of idiocy have not yet been fully made out. It is unquestionably hereditary in at least 50 per cent. Consanguine marriages are the cause of idiocy beyond doubt, but only when the stock is bad, and so any tendency to nervous disease in the parents is doubled in the children. Scrofula is another fertile source of this degeneration of humanity, and there is ground to believe that frights to the mother when pregnant cause a small proportion of the idiocy of the world. But idiots are born in apparently perfectly healthy families. Evolutionally idiocy, imbecility, and cretinism may be looked on as reversions to a lower type, and so an example of one of nature's ways of bringing a bad stock to an end by stopping reproduction. Idiots and imbeciles are regarded as children all their days by the law, and provisions are made for the appointment of tutors and curators for them. They are held irresponsible for their acts. See Dr W. W. Ireland, Idiocy and Imbecility (1877).