434 THE POPULAR SCIENCE MONTHLY. 



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 recog-' 

 nize 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 my- 

 self 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 con- 

 tinuously for ten years, as he was during his whole life, with qualita- 

 tive 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 diplo- 

 matist, jurist and physician, mathematician and descriptive naturalist, 

 chess-player and mechanician all are practiced in their peculiar meth- 

 ods 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 prac- 

 tice 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 explana- 

 tion of consciousness even in its simplest form, will never think ulti- 

 mately 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 mole- 

 cules in a gasometer to perform their crossings and reboundings ; and 

 we may even confidently anticipate an important result, just the al- 

 ready 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- 



