CHAPTER V.

CONCLUSION.

To describe the various diseases of memory, and to seek to determine the law which governs their evolution, has been our endeavor up to this point. In conclusion, something should be said with regard to causes of immediate organic causes, that is. Even when reduced to these terms, the etiology of diseases of memory is very obscure, and what is definitely known concerning it may be stated in very brief space. Memory consists of a conservation and a reproduction: conservation seems to depend especially upon nutrition; reproduction upon general or local circulation.

I.

Conservation, which is, on the whole, the more important of these two functions, since without it reproduction is impossible, supposes a primary condition that can only be expressed in the vague phraseology, "a normal constitution of the brain." We have seen that idiots are the subjects of con

genital amnesia, of an innate inability to fix impressions. This first condition is, therefore, a postulate; it is less a condition of memory than an essential condition of the existence of memory. It is found, in fact, in all persons of a healthy mental state. This normal constitution being granted, it is not enough that impressions be received; they must be fixed, organically registered, conserved; they must produce permanent modifications in the brain; the modifications impressed upon the nerve-cells and -filaments, and the dynamic associations which these elements form must be stable. This result can depend only on nutrition. The brain, and particularly the gray substance, receives an enormous amount of blood. There is no portion of the body where the work of nutrition is more complete or more rapid. We are ignorant of the special mechanism of this work. Histology can not follow molecular changes. We can only observe effects; all the rest is hypothesis. But there are facts enough to prove the direct relation between nutrition and the memory.

That children learn with marvelous facility, and that everthing depending upon memory, such as the acquirement of a language, is easily mastered by them, is a matter of common observation. We also know that habits (a certain form of memory) are more readily acquired in childhood and youth than in after-life. At the former

period the activity of the processes of nutrition is so great that new associations are rapidly established. In the aged, on the contrary, the prompt effacement of new impressions coincides with a notable diminution of this activity. What is quickly learned is soon forgotten. The expression "to assimilate knowledge" is not a metaphor. The psychical fact has an organic cause. For the fixation of recollections, time is necessary, since nutrition does not do its work in a moment; the incessant molecular movement of which it is composed must follow a constant path in order that an impression periodically renewed may be maintained.*

"A distinguished theatrical performer," says Abercrombie, "in consequence of the sudden illness of another actor, had occasion to prepare himself, on very short notice, for a part which was entirely new to him; and the part was long and rather difficult. He acquired it in a very short time, and went through it with perfect accuracy, but immediately after the performance forgot every word of it. Characters which he had acquired in a more deliberate manner he never forgets, but can perform them at any time without a moment's preparation; but, in regard to the character now mentioned, there was the further and very singular fact that, though he has repeatedly performed it since that time, he has been obliged each time to prepare it anew, and has never acquired in regard to it that facility which is familiar to him in other instances. When questioned respecting the mental process which he employed the first time he performed this part, he says that he lost sight entirely of the audience, and seemed to have nothing before him but the pages of the book from which he had learned it; and, that if anything had occurred to interrupt the illusion, he should have stopped instantly." (Op. cit., p. 103.)

Fatigue in any form is fatal to memory. The received impressions are not fixed; reproduction is slow, often impossible. Fatigue is a result of superactivity in an organ by which nutrition suffers and languishes. With a return to normal conditions memory returns. The incident related by Holland, cited in a previous chapter, offers explicit testimony upon this point. We have also seen that, in cases where amnesia follows cerebral shock, forgetfulness is always retrograde, extending over a more or less protracted period, previous to the accident. Most physiologists who have given attention to this phenomenon explain it as resulting from defective nutrition. Organic registration, which consists in a nutritive modification of the cerebral substance, is for some reason wanting. Finally, it should be remembered that disease of memory in its gravest form-progressive amnesia of dementia, old age, or general paralysis-is caused by an increasing atrophy of the nervous elements. The capillaries and cells undergo degeneration; the latter finally disappear, leaving in their place only ineffective débris.

These facts-physiological and pathological— show that there is between nutrition and conservation the relation of cause and effect. There is an exact coincidence in the periods of culmination and decline. Variations, short or long, in one, have corresponding variations in the other.

If one be active, or moderate, or languishing, the other is similarly affected. Conservation of impressions must, therefore, be conceived not in a metaphysical sense as "a faculty of the mind,' existing no one knows where, but as an acquired state of the cerebral organism which implies the possibility of conscious states when their condi tions of existence are fulfilled. The extreme rapidity of nutritive changes in the brain, which at first thought would seem to be a source of instability, is in reality the cause of the fixation of recollections.

"The waste following activity is restored by nutrition, and a trace or residuum remains embodied in the constitution of the nervous center, becoming more complete and distinct with each succeeding repetition of the impression; an acquired nature is grafted on the original nature of the cell by virtue of its plastic power.' "* We here touch the primal meaning of memory as a biological fact: it is an impregnation. Hence it is not surprising that the eminent English surgeon, Sir James Paget, in treating of the permanent modifications made in the living tissues by contagious diseases, should express himself in the following terms, particularly applicable to our discussion: "It is asked," he says, "how can the brain be the organ of memory when you : *Maudsley, "Physiology and Pathology of the Mind," p. 91.