116 PSYCIIOLOGT. 



regions of brain and mind are set comparatively free, 

 diagram will make the matter clear : 



Let Ay B, C, D, E, F, G represent an habitual chain of 

 muscular contractions, and let a, b, c, d, e, f stand for the 

 respective sensations which these contractions excite in us 

 when they are successively performed. Such sensations 

 will usually be of the muscles, skin, or joints of the parts 

 moved, but they may also be effects of the movement upon 

 the eye or the ear. Through them, and through them 

 alone, we are made aware wdiether the contraction has or 

 has not occurred. When the series. A, B, C, D, E, F, G, is 

 being learned, each of these sensations becomes the object 

 of a separate perception by the mind. By it we test each 

 movement, to see if it be right before advancing to the next. 

 We hesitate, compare, choose, revoke, reject, etc., by intel- 

 lectual means ; and the order by which the next movement 

 is discharged is an express order from the ideational centres 

 after this deliberation has been gone through. 



In habitual action, on the contrary, the only impulse 

 which the centres of idea or perception need send down is 

 the initial impulse, the command to start. This is repre- 

 sented in the diagram by F; it may be a thought of the 

 first movement or of the last result, or a mere perception 

 of some of the habitual conditions of the chain, the presence, 

 e.g., of the keyboard near the hand. In the present case, 

 no sooner has the conscious thought or volition instigated 

 movement A, than A, through the sensation a of its own 

 occurrence, awakens B reflexly ; B then excites C through 

 b, and so on till the chain is ended, when the intellect gen- 

 era.lly takes cognizance of the final result. The process, in 

 fact, resembles the passage of a wave of ' peristaltic ' motion 



