_Failure of Memory accompanies failure of mental Power._--A decline of mental vigor, whether produced by disease or age, is usually attended with loss of memory to some extent. The first symptoms of this failure are usually forgetfulness of proper names and dates, and sometimes of words in general. A stroke of palsy frequently produces this result, and in such cases the name sometimes suggests the object, while the object no longer recalls the name. This is probably owing to the fact that the sign, being of less consequence than the thing signified, and making less impression on the mind, is more readily forgotten; hence the name, if suggested, recalls the thing, while, at the same time, the thing may not recall the name. In general, we pass more readily from the sign to the thing signified, than the reverse, and for the reason now given. Mr. Steward remarks, that this loss of proper names incident to old men, is chiefly observable in men of science, or those much occupied with important affairs--a fact resulting, he thinks, partly from their habits of general thought, and partly from their want of constant practice in that trivial conversation which is every moment recalling particulars to the mind.
_The Memory of the Aged._--In the principles which have been advanced, we find an explanation, I think, of some facts respecting memory, which every one has noticed, but of which the philosophy may not be at first sight apparent, Why is it that aged people forget? that, as we grow old, while perhaps other powers of the mind are still vigorous, the memory begins to lose its tenacity? Not, I suspect, from any special change which the brain undergoes, for why should such changes affect _this_ faculty more than any other? I should seek the explanation in a failure of one or other of the conditions already mentioned as essential to a good memory; either in the want of a sufficiently frequent coëxistence of associated ideas, or else in the want of a sufficiently vivid conception of them when presented; or, more likely, in both. And so the facts would indicate. Age involves usually the gradual failure and decay of the powers of perception; the ear fails to report what is said, the eye what is passing in space; and as memory is dependent on prior perception, of course a diminished activity of the one brings about a diminished activity of the other. In proportion as this ensues, the mind's interest in passing events is likely to fail, for what is no longer clearly apprehended no longer awakens the same interest and attention as formerly. This directly affects the vividness of conception, and indirectly also reacts upon the frequency of coëxistence, for what we do not clearly apprehend, nor feel much interest in, will not be likely often to recur to mind, nor shall we dwell upon it when presented. There is thus brought about, by the mutual action and reaction of the causes now specified, a failure more or less complete of the essential conditions of a retentive memory.