combined, which results from the prolonged exercise of it: and it is especially in our inability to recollect something which we wish to call to mind, that this failure of power shows itself. An interval of repose completely restores the power, obviously (to the mind of the Physiologist) by the renovation of the worn-out Brain-tissue, and by the purification of the Blood that has become charged with the products of its "waste."—The impairment of the Memory in Old Age commonly shows itself in regard to new impressions; those of the earlier period of life not only remaining in full distinctness, but even, it would seem, increasing in vividness, from the fact that the Ego is not distracted from attending to them by the continual influx of impressions produced by passing events. The extraordinary persistence of early impressions, when the Mind seems almost to have ceased to register new ones, is in remarkable accordance with the Law of Nutrition referred to in a previous paper. It is when the Brain is growing, that the direction of its structure can be most strongly and persistently given to it. Thus the Habits of Thought come to be formed, and those Nerve-tracks laid down which (as the Physiologist believes) constitute the Mechanism of Association, by the time that the Brain has reached its maturity; and the Nutrition of the organ continues to keep up the same mechanism, in accordance with the demands upon its activity, so long as it is being called into use. Further, during the entire period of vigorous Manhood, the Brain, like the Muscles, may be taking on some additional growth, either as a whole, or in special parts; new tissue being developed and kept up by the nutritive process, in accordance with the modes of action to which the Organ is trained. And in this manner a store of "impressions" or "traces" is accumulated, which may be brought within the "sphere of consciousness" whenever the right suggesting-strings are touched. But, as the Nutritive activity diminishes, the "waste" becomes more rapid than the renovation; and it would seem that, while (to use a Commercial analogy) the "old-established houses" keep their ground, those later firms whose basis is less secure, are the first to crumble away—the Nutritive activity, which yet suffices to maintain the original structure, not being capable of keeping the subsequent additions to it in working order. This earlier degeneration of later-formed structures is a general fact perfectly familiar to the Physiologist.
The effects of Disease and Injury on the Memory are so marvellous and diverse, that only a very general indication of them can be here given. Cases are very common, in which the form of impairment just spoken of as characteristic of Old Age shows itself to a yet greater extent; the Brain being so disordered by attacks of Apoplexy or Epilepsy (for example), that it seems altogether incapable of retaining any new impressions, so that the patient does not remember any thing that passes from day to day; while the impressions of events which happened long before the commencement of his malady recur with
