Great confusion exists in the public mind as to the nature of idiocy. What is an idiot? Dr. Séguin, a celebrated writer on this subject, has described idiocy as a "specific infirmity of the cerebro-spinal centre," a definition which I need not say applies to a variety of infirmities to which flesh is heir, and such a definition only serves as a cloak for ignorance. Shakespeare, that wonderfully accurate observer of human nature, in several of his dramas has given a very good description of the acts of the idiot, who, he says, is "one who holds his bauble for his God;" and again, as "one who tells a tale full of sound and fury, signifying nothing." But neither he nor the psychologists of his day knew enough of the natural history of the idiot to attempt a logical definition. As I have spent a great deal of time in the investigation of obscure points of cerebral pathology, of course the question of the idiot has not escaped my attention, and I submit the following definition:-- An idiot is a human being who possesses the tripartite nature of man--body, soul, and spirit, σωμα, ψυχη, πνευμα, but who is the subject of an infirmity consisting, anatomically, of a defective organisation and want of development of the brain, resulting in an inability, more or less complete, for the exercise of the intellectual, moral, and sensitive faculties. There are various shades and degrees of this want of development, from those whose mental and bodily deficiencies differ but slightly from the lowest of the so-called sound-minded, to those individuals who simply vegetate, and whose deficiencies are so decided as to isolate them, as it were, from the rest of nature. Dr. Langdon Down[1] divides Idiocy into three primary groups: Congenital, Developmental, and Accidental. The Congenital includes all cases which at the period of birth manifest signs of the defective mental power. The Developmental group includes cases where the child manifests an average intelligence through infancy, but he is born with a proclivity to a mental break-down during one of the developmental crises, such as the first dentition, the second dentition, and puberty; the brain and nervous power are sufficient for their early years, but are insufficient to carry them through evolutional stages. The Accidental group includes cases where the child has been born with a normal nervous system, when unfortunately a fall, a fright, epilepsy, or some other cause may lead to a mental break-down, not of a genetic, but of a purely accidental origin. The various forms of idiocy are described in minute detail by Dr. Ireland,[2] to whose classical work I would refer those who may desire further information on this subject.