Memory

is said to be exeecised, a any thought of the mind, or image of an external object preserved in the sentient part of the brain, excites any perception in the mind. This is commonly weaker than in imagination, and almost confined to certain arbitrary signs, which the mind conjoined with that idea at its first precept i on. For memory hardly represents the images and pictures of things to the mind, but almost only words, and certain attributes, and abstract ideas 3 for which reason it excites volition le powerfully... But it appears from the observation of the phoenomena ef memory, that those charges which arise from the external senses, remain long in the brain; and sometimes, if they made a strong impre ion, are represented to the mind for a long period, almost for ever; but that they are gradually weakened and impaired; unle they be renewed, either by the object being represented again to the mind, or by the mind itself recalling the same change again into memory; and that at last the change will be in a manner erased, and entirely lost, and the idea which was connected with that change by the law of nature will never again recur to the mind. This. annihilation gradually effected by new and different impre ions made on the sensorium, and not from time only, or the circulation of the blood, as in cataleptic patients, who sometimes after a considerable interval of time, return to the same train of thought which the disease had interrupted. But sometimes all of them will be suddenly destroyed by some disease, in which the brain is in some way compre ed, either by the blood or any other cause, Such a cause, acting on part of the com~- mon sensory, blots out a part of the impre ions from the memory, such as certain words, or all of them, the characters by which we expre words, or our friends, and even the nece aries of lifes yet all these impre ions may often be renewed by removing the compre ing cause. But the strength and duration ef an idea depend upon its being unusual, exce ive, or greatly conducing either to increase or le en felicity; and lastly, upon our attention to it, and repetition; which last renders the impre ions so vivid, that their perception is at length mistaken by the mind for the perception of external objects, as in the case of maniacs. Moreover, if we review the history of human life, it appears that in early infancy we have hardly any memory; only simple perceptions, that soon, vanish: which, neverthele ,. excite strong ideas in the mind, as we see from the crying of infants. The memory is perfected by degrees, and the ideas received from favourite objects, and familiar persons, remain impre ed in the mind of the infant; while at the same tine, the imagination likewise increases, Which is_ ofter very powerful in young children; as for example, in terror, which in no age produces more violent or deplorable effects. Afterwards, as the number of our ideas increases, the facility of preserving past ideas is impaired, and, at the same time, the power of the imagination becomes torpid; till at last the former almost perishes, and the ideas which are received escape from the brain in a short times; while at the same time, the imagination, which is a kind of memory, languishes. But since these pereeptions produce various changes in the mind itself, which are perfectly distinct from any corporeal faculty, we shall briefly add something concerning them, so far as may suffice for the purposes of medicine. Thought resides in the soul, it attends to the sensations which are either brought by the senses, or recalled by the imagination; frequently also to the mere signs which recur into the mind. Attention is when one idea occupies the mind principally or solely for any length of time. The comparison of two ideas, instituted by the mind, is called judgment or genius, when the mind, by comparing them, discovers them to be alike or di imilar. Genius consists in a vivid sensation conjoined with rapidity of thought, so as instantly to abstract from notions their points of similitude and di imilitude. The principal source of judgment, invention, and wisdom, consists in the slow examination of ideas, by which they are considered by the mind in every point of view, and in the attention of the mind being confined to one object, to the exclusion of all other ideas. Hence the efficacy of darkne in making difficult caiculations; the exquisite attention of blind people to the nature of sounds, and of those who are deaf, to colours. The sources of error are negligence in contemplating the whole idea, the estimating it from a partial view, and the connection of ideas with others that are distinct, and only related by accident, or external causes, The integrity of the judgment depends upon a healthy constitution of the brain. For when that is compre ed, irritated, exhausted of blood, or changed in its fabric, the use of reason is totally disturbed; the strong internal impre ions on the brain are represented to the mind as external or real objects; the chain of ideas is broken, so that the mind does not compare them, or perceive their resemblance or diversity, but pa es abruptly from one idea to another totally different; lastly, the actions of the senses being impaired or interrupted, and all impre ions being in a manner erased from the brain, man is reduced to a state of imbecility or vegetation. But external causes also have considerable influence in changing the relation of the mind to the impre ions of the ‘senses; the air, way of life, food, and habit, either a ist or diminish the soundne of the judgment, the force of the imagination, and the ‘strength of the memory.