APPENDIX I 287 



conscious voluntary movements, conscious involun- 

 tary movements, for we pass gradually to 

 unconscious involuntary movements, due (as 

 we say) to reflex action of the nervous 

 system. A conscious voluntary movement may 

 by repetition become unconscious, and even 

 involuntary; this we call "habit." A habit 

 is unconscious action acquired by an individual. 

 Instincts are inherited habits, brought nearly to per- 

 fection by natural selection. Thus all the vital 

 processes of our bodies, such as breathing and the 

 action of the heart, are instinctive. They are so 

 regular that they give the idea of being mechanically 

 performed ; but the appearance is deceptive, and they 

 differ fundamentally from all purely mechanical 

 motion. Physical energy, when it acts for the first 

 time , acts as efficiently and with as great certainty as 

 if it had performed the action many times ; there is 

 no improvement. But with physiological actions 

 the case is very different. The first movements are 

 tentative ; and it is only after constant repetition that 

 they become decisive and prompt, like those due 

 to physical energy. Even then they do not always 

 remain constant ; for, it is well known, instincts may 

 sometimes be altered by a little dose of reason that 

 is, by the attention of the animal being called to 

 them. It must therefore be allowed that these 

 pseudo-mechanical movements, although now be- 

 yond the control of the will, originated in voluntary 

 movements', and that, however rigidly they now 

 act, they have been imposed on the organism by a 

 long line of ancestors. We must also suppose that 



