upon his mind, others passed out. The morphologist remembers forms, the mathematician formulas, though he may prefer to work them out anew; the philologist speech-forms and citations, the chess-player games. Personages whose high positions in life require them to recognize many faces have wonderful accomplishments in that faculty. I have myself learned from my own experience that the same person by changing his employment may, if we may use such an expression, change the direction of his memory. I have also observed upon myself the influence of exercise upon the memory. Faraday was, it is well known, accustomed to lament the weakness of his memory. And when I (if I may compare small things with great) was engaged continuously for ten years, as he was during his whole life, with qualitative experiments, I remarked that my former good memory declined, undoubtedly because I needed each day, to continue my work, only the steps of the experiments of the day before. My memory began to improve again when I began to give lectures. Like the memory, the power of the most various mental activities increases with exercise and diminishes with neglect. We hear a great deal said in teachers' associations about how school-youth should not only appropriate what is taught them, but should also learn to exercise their sensations and perceptions, and make their mental powers facile. General and diplomatist, jurist and physician, mathematician and descriptive naturalist, chess-player and mechanician all are practiced in their peculiar methods of thought. The effects of exercise extend into the emotional life: who would doubt that a Heine exercised himself in giving free course to the flow of his conceptions, in allowing them to strengthen themselves, as it were, in order to draw half deliberately out of the fountain the immortal complaint of self-created sorrow?
There are in psychology few darker points than the doubling of our I in this mental exercise. A final incomprehensible something in us oppose as subject another equally Incomprehensible as object, which is ourselves, yet also really is not, and forces it to a painful exertion, as at another time it compels its bodily substratum to practice itself in a composite movement, with aching muscles and other pains. Whoever comprehends the fundamental fact of metaphysics, that no arrangement and movement of matter can afford an explanation of consciousness even in its simplest form, will never think ultimately of conceiving these processes as mechanical ones.
This confessedly does not exclude our at least ideally, looking through to the play of the ultimate atoms of our present elements, somewhat as Herr Clausius, before our mental eyes, causes the molecules in a gasometer to perform their crossings and reboundings; and we may even confidently anticipate an important result, just the already declared fundamental distinction between exercise of the central nerve-system and exercise of the muscles, connective substances, etc. While in these tissues we deal with nutritive and formative stimu-
