112 PSTCHOL007. 



the latter in terms of brain — the universally admitted fact that any 

 sequence of mental action which has been frequently repeated tends to 

 perpetuate itself ; so that we tind ourselves automatically prompted to 

 think, feel, or do what we have been before accustomed to think, feel, 

 or do, under like circumstances, without any consciously formed pur- 

 pose, or anticipation of results. For there is no reason to regard the 

 cerebrum as an exception to the general principle that, while each part 

 of the organism tends io form itself in accordance with the mode in 

 which it is habitually exercised, this tendency will be especially strong 

 in the nervous apparatus, in virtue of that incessant regeneration which 

 is the very condition of its functional activity. It scarcely, indeed, 

 admits of doubt that every state of ideational consciousness which is 

 either very strong or is habitually repeated leaves an oi'ganic impres- 

 sion on the cerebrum ; in virtue of which that same state may be re- 

 produced at any future time, in respondence to a suggestion fitted to 

 excite it. . . . The ' strength of early association ' is a fact so 

 universally recognized that the expression of it has become proverbial ; 

 and this precisely accords with the physiological principle that, during 

 the period of growth and development, the formative activity of the 

 brain will be most amenable to directing influences. It is in this way 

 that what is early ' learned by heart ' becomes branded in (as it were) 

 upon the cerebrum ; so that its ' traces ' are never lost, even though 

 the conscious memory of it may have completely faded out. For, when 

 the organic modification has been once fixed in the growing brain, it 

 becomes a part of the normal fabric, and is regularly maintained by 

 nutritive substitution ; so that it may endure to the end of life, like the 

 scar of a wound." 



Dr. Carpenter's phrase that our nervous system groios to 

 the modes in wMcli it has been exercised expresses the philos- 

 ophy of habit in a nutshell. We may now trace some of 

 the practical applications of the principle to human life. 



The first result of it is that hghit siuiplifp.^ flie mnvprnnifs 

 required to achievejt^ijmijresulj^^ uccuratt 



! and diminishes fatigue. 



"The beginner at the piano not only moves his finger up and down 

 in order to depress the key, he moves the whole hand, the forearm and 

 even the entire body, especially moving its least rigid part, the head, 

 as if he would press down the key with that organ too. Often a con- 

 traction of the abdominal muscles occurs as well. Principally, however, 

 the impulse is determined to the motion of the hand and of the single 

 finger. This is, in the first place, because the movement of the finger 

 is the movement thought of, and, in the second place, because its move- 

 ment and that of the key are the movements we try to perceive, along 

 with the results of the latter on the ear. The more often the process 



