Page:Popular Science Monthly Volume 7.djvu/681

Rh others. And this convinces me that there is yet a higher philosophy on this subject which I have not reached.

—We are all familiar with this process. A movement or series of movements at first painfully difficult, and requiring the whole thought and attention, by repetition become so easy and semi-automatic that attention is no longer necessary. The most remarkable examples of these, such as walking, speaking, and the like, probably belong partly to the third category; the capacity for these is partly inherited. Playing on a musical instrument is therefore a better example. We all know the painful attention necessary at first, and the ease and rapidity of the most complex movements attained by practice. Now, by what means, anatomical or physiological, do these at first difficult movements become by repetition easy? The answer in general terms seems to be this: Every volitional act is attended with a change in the brain, which, however, is slight, liable to be effaced by subsequent changes, and therefore evanescent. If the same act, however, be repeated many times, the change becomes deep and permanent—becomes petrified in brain-structure; and this structure, whatever be its character or its seat, determines the appropriate acts with precision. It is as if every volitional act produced a faint line, liable to be erased, on the tablet of the brain; by running over the same lines many times, these are deepened into grooves and finally into ruts, and motion in these becomes easy and certain because the ruts guide the motion instead of the will. Thus repetition produces structure and structure determines habit.

—The structure produced by repetition of voluntary acts, and which, as we have seen, determines habits, by the law of inheritance is transmitted in a slight degree to the next generation. I say in a slight degree only, because inheritance is from the whole line of ancestry and not from the immediate parents alone. The inheritance from the immediate parents is greater, it is true, than from any one of the series of previous generations, but infinitely less than the sum of inheritances from all previous generations. The structure may be regarded, therefore, as transmitted in an almost effaced condition. If the same acts are not repeated, the lines of structure are soon wholly effaced by new lines running across the tablet in all directions; but if they are repeated the same lines are deepened with greater ease and certainty than before; the structure becomes still more decided, the habit still more fixed. This more deeply-engraved structure is again partially transmitted to be again strengthened in the next generation—the engraved plate is retouched and the lines deepened. Thus with every generation the sum of inheritance becomes greater because from a greater number of preceding generations; with every generation the effacement by transmission is less, and the deepening by repetition is greater, until finally a highly-differentiated structure is formed, and perfectly transmitted—a structure