fears are made to depend upon symbols. No particular account is therefore required for these phænomena; they are strictly natural; and many of the chief reasons for the imperfection of the memory and judgment in children occurring perpetually, and being very obvious, it is not usually supposed, that any particular account is required. However, if an adult should become subject to a like erroneousness, it would evidently be one species of madness; as fatuity or idiotism is. Here the brain labours under such an original disorder, as either not to receive a disposition to the miniature vibrations in which ideas consist, and whence voluntary motions are derived, but with great difficulty; or if it receive such dispositions readily, they have not the usual permanency; in both which cases it is evident, that the memory, with all the faculties thereon depending, must continue in an imperfect state, such as is observed in idiots. The want of the connecting consciousness in children and idiots, and indeed in maniacs of various kinds, excites our pity in a peculiar manner, this connecting consciousness being esteemed a principal source and requisite of happiness. Their helplessness, and the dangers to which they are exposed without foreseeing them, contribute also to enhance our compassion.
The dotage of old persons is oftentimes something more than a mere decay of memory. For they mistake things present for others, and their discourse is often foreign to the objects that are presented to them. However, the imperfection of their memory in respect of impressions but just made, or at short intervals of past time, is one principal source of their mistakes. One may suppose here that the parts of the brain in which the miniature vibrations belonging to ideas have taken place, are decayed in a peculiar manner, perhaps from too great use, while the parts appropriated to the natural, vital, and animal motions remain tolerably perfect. The sinuses of the brain are probably considerably distended in these cases, and the brain itself in a languishing state; for there seems to be a considerable resemblance between the inconsistencies of some kinds of dotage, and those of dreams. Besides which it may be observed, that in dotage the person is often sluggish and lethargic; and that as a defect of the nutritive faculty in the brain will permit the sinuses to be more easily distended, so a distention of the sinuses, from this or any other cause, may impede the due nutrition of the brain. We see that, in old persons, all the parts, even the bones themselves, waste and grow less. Why may not this happen to the brain, the origin of all, and arise from an obstruction of the infinitesimal vessels of the nervous system, this obstruction causing such a degree of opacity, as greatly to abate, or even to destroy, the powers of association and memory? At the same time vibrations,
