Insanity, in the most comprehensive acceptation of the term, implies a mental ineptitude for conducting one's self in the management of private concerns and in the relations of social life. Great deficiencies and aberrations, indeed, often exist, which are never denominated insanity. There is generally a difference of physiognomy and manner which, in addition to what may be called unaccountable peculiari ties of conduct, authorise us in pronouncing a man insane, and this, though readily recognised by persons of observa tion, does not admit of definition.
Insanity exists in various forms, as well as various de grees. NVhen we attempt to establish a division of the sub ject on the forms which it assumes, our subdivisions be come too numerous, and we run the risk of substituting symptoms which are liable to great and rapid interchange in the same individuals, for different species and descrip. lions of disease.
The most convenient division of the subject, is that which is founded on the origin of different cases of insanity. There is a marked difference between " congenital" and supervening insanity." The congenital variety is one from which no recovery is expected. It is generally de nominated idiotism, and is usually distinguished by a defi ciency, rather than a derangement of the mental powers. Some one of the senses is often at the same time dull or abolished. This happens most frequently with that of hearing. The want of a power of giving attention is the most glaring symptom ; and this is distinguished Irom the volatility of lively minds, by being accompanied with a slow ness or inability to form combinations among the ideas of perception, or to draw silent practical inferences for the their actions. It is readily known by a pecu liar look and manner, accompanied with an aliena tion from all the feelings and pursuits of other persons, an insensibility to those impressions which are derived from social intercourse, and an ineptitude to receive instruction. Sometimes the idiot never learns to speak, and his articu lation is always imperfect. He seems insensible to the language of others, and only occasionally perceives a rude glimmering of meaning in words or expressions which have received an habitual association with the supply of his na tural wants, or the excitement of strong feelings of bodily pleasure or pain. Yet there are remarkable instances of partial idiotism. Monstrous deficiencies are conjoined with great quickness, great address, tenacious memory, and even symptoms of genius. These qualifications are limit ed, however, to a narrow range of objects.
Yet congenital insanity has sometimes assumed a form more nearly allied to the madness which attacks adults. Children have been known who, without those deficiencies commonly reckoned idiotism, have evinced a degree of estrangement from their species, an insensibility to all kind ness and good humour, and a perpetual proclivity to the most unprovoked malice, and to the most violent forms of outrage, in a form equally incorrigible and conspicuous as in the most dangerous maniacs, Two remarkable cases of this kind are described by Mr. Haslam. \Ve also occa
sionally see natural idiots, who have a degree of activity which assimilates their character more or less to that of other insane persons. On the other hand, an imbecility ex actly similar to that of natural idiots has often originated, from various causes, in persons who had pieviously been in full possession of their faculties. It is only a prevailing, it is not an universal fact, that congenital insanity assumes the form of idiotism, and supervening insanity that to which we give the name of madness.
To trace the connection between deficiencies of mind and defects or disorders of organization, is not an easy task. Nature invites us to it by some prevailing coincidences ; but, when we trace these down to their minutiae, she leaves us in the midst of such mere conjecture and uncertainty, that we find it difficult to determine the point at which our researches become unavailing. Idiots are evidently dis tinguished from other persons by a peculiarity in the ap. pearance of the head. Most commonly the head is of di minutive size, awl that part of the brain which lies be tween the forehead and the vertex, is small in quantity. At other times, the back part of the head appears defi cient ; the boundary of the occiput is a vertical line in con tinuity with that of the cirvix, and the anterior part of the head is towering and heavy. Some who have professed to prosecute the subject extensively, have told us that these were cases in which the ventricles of the brain were distend ed with a serous secretion, and the cerebral substance both deficient in quantity, and subjected to all the disadvantages arising from dropsical oppression and disorganization. Tnis has been declared to be universally the case with idiots, whose heads either exhibited this particular shape, or were preternaturally large. These observations have not yet been sufficiently extensive, and attested by a sufficient num ber of observers, to form a part of the ascertained doc trines of science. This is no derogation from the credit due to the enterprise of those who have undertaken them ; who, though they may not be trusted as superior to the in fluence which enthusiasm sometimes exercises over the power of observation, deserve praise for their devotedness to the object, and will be entitled to more lasting honour, if even a few of their positions shall be ultimately establish ed. Casts of the heads of idiots whose cases are minutely described, and whose brains have been dissected after death, if multiplied and well authenticated in different countries, cannot fail ultimately to throw much light on the nervous system, and its connection with the manifestations of the mind. Yet it is possible that the conclusions ob tained may widely differ from any that have been hitherto anticipated.