MENTAL PHYSIOLOGY, 



171 



perience, so that they could be foretold with 

 certainty if this experience were fully known. 

 But in man, over and above all which the lower 

 animals possess, there is also a true volition, 

 rudimentary enough in many instances, but capa- 

 ble of great development in two different direc- 

 tions — first, as an inhibitory power, to restrain 

 cither reflex or sensorial or ideo-motor impulses 

 from going out in action — to hold the machine 

 of the body still in spite of them ; secondly, as a 

 selecting power, to retain certain ideas before 

 the consciousness to the exclusion of others, to 

 "dwell" upon them by deliberate choice, and 

 thus to derange the balance of mere experience, 

 and to give to the selected ideas an increased 

 weight in determining the conduct. When the 

 merely restraining action of the will is removed, 

 and the idea is suffered to work itself out in 

 action, such action is said to be " voluntary ; " 

 but when the will is employed to maintain and 

 continue a selected course, the action is then said 

 to be " volitional." 



We have already seen that sensorial impulses, 

 wheD constantly directed into some definite chan- 

 nel, lead to acquired instincts ; and these in time 

 become, if not irresistible, yet nearly as powerful 

 as the instincts which were original. A practised 

 musician was once a learner who had to acquire 

 finger-movements singly, slowly, and laboriously. 

 He arrives in time at a condition in which he is 

 unconscious of what his hands are doing, and in 

 which he simply permits the visual sensations 

 derived from the printed notes, or the ideas lin- 

 gering in his memory, to run away with his mus- 

 cles as they will. The change is believed to de- 

 pend on a distinctly structural change in the 

 nerve-centres, which have " grown to " a certain 

 method of activity ; and hence, probably, it is 

 wrought most easily in early life, when the struct- 

 ures of the body have a greater capacity for de- 

 velopment than that which they afterward retain. 

 What applies in this way to the sensorial centres 

 applies likewise to the cerebrum ; and the power 

 to select from among the ideas which offer them- 

 selves to the consciousness, as well as the facility 

 of dwelling upon particular classes of ideas, in- 

 creases rapidly under the influence of well-di- 

 rected effort. Dugald Stewart, though he was 

 not guided by the light of modern physiology, 

 was well aware of the difference between voli- 

 tional and automatic attention. The condition 

 of learning anything, and especially of learning 

 anything which is not of itself attractive to the 

 learner, is one of volitional attention ; and this, 

 like most other forms of volitional effort, is both 



fatiguing and intermittent. Dugald Stewart point- 

 ed out, moreover, that what we are conscious of 

 in such circumstances is not our attention to the 

 subject-matter, but only our lapses of attention, 

 and our efforts to bring back the thoughts to 

 points from which they perpetually wander. 

 When the pursuit is inherently attractive, the at- 

 tention paid to it becomes automatic, the thoughts 

 have no tendency to wander, and no conscious- 

 ness of effort or of fatigue is experienced. Be- 

 tween these two stales there is an intermediate 

 one, in which the direction of the thoughts, at 

 first purely volitional, intermittent, and fatiguing, 

 is rendered daily more and more easy by con- 

 stantly-recurring habit, and becomes at last a 

 second nature to the individual. 



On the basis of the principles which are thus 

 sketched in the barest outline, and by the aid of 

 a variety of illustrations derived from the daily 

 conduct of mankind — illustrations which, when 

 taken singly, are often trivial, but which in most 

 cases so fit into the mosaic of the argument as to 

 complete a pattern of great symmetry and beau- 

 ty — Dr. Carpenter has built up a natural history 

 of the mental faculties which will fully repay the 

 most careful study that can be bestowed upon it. 

 His account of " Memory," of " Common-Sense," 

 of " Unconscious Cerebration," and cf "Reverie 

 and Somnambulism," will be absolute revelations 

 to the great majority of readers ; and, when once 

 certain preliminary details have been mastered, 

 the facts and arguments upon which he relies are 

 stated and explained with a freedom from techni- 

 calities, and with a pellucid clearness of thought 

 and diction, which leave nothing on either score 

 to be desired. Of equal temporary, although of 

 less abiding interest, are the chapters in which 

 he analyzes the marvels described under the 

 names of "biology" and " spiritualism," chap- 

 ters which withdraw these marvels wholly from the 

 domain of the supernatural, and arrange them, 

 as far as they may be assumed to be real, under 

 their proper places in a system which takes note 

 of the aberrations and perturbations as well as 

 of the health and normal acts of the uervous ap- 

 paratus of mankind. We must observe, however, 

 that it will for most persons be wasted labor to 

 turn to these portions of the volume until those 

 which precede and lead up to them have been 

 perused with due attention, since the former con- 

 tain the keys by which alone the latter can be 

 unlocked. Until the mechanism of the ordinary 

 varieties of mental action is fully understood, it 

 will be generally useless to attempt the compre- 

 hension of varieties which are more intricate. 



