SYMMETRY AND HARMONY OF MUSCULAR MOVEMENTS. 911 



actions to the performance of some new kind of movement as in the case of an 

 infant learning to walk, a child learning to write, an artisan learning some oc- 

 cupation which requires nice manipulation, a musical performer learning a new 

 instrument, and so on is found, when attentively studied, to indicate that the 

 Will is far from having that direct and immediate control over the contractions 

 of the Muscles which it is commonly reputed to possess ; and that the operation 

 really consists in the gradual establishment of a new grouping of the separate 

 actions, in virtue of which the stimulus of a Volitional determination, acting 

 under the guidance of the muscular sensations, henceforth calls into contraction 

 the group of muscles whose agency is competent to carry that determination 

 into effect. For however amenable any set of muscles (as those of the arm and 

 hand) may have become to the direction of the Will, in any operations which 

 they have been previously accustomed to perform, it is only after considerable 

 practice that they can be trained to any method of combined action which is 

 entirely new to them ; and even if we attempt to bring our anatomical know- 

 ledge into use for such a purpose, by mentally fixing upon certain muscles whose 

 action we wish to intensify and to associate with those of others, we find that 

 such a method of proceeding affords no assistance whatever, but rather tends to 

 impede our progress, by drawing off the attention from the " guiding sensations" 

 (visual, muscular, &c.), which are the only regulators that can be depended 

 upon for determining the due performance of the volitional mandate. Hence 

 we are led by these considerations, as by those stated in the preceding paragraph, 

 to the conclusion, that the agency which directly affects the muscles is of the 

 same kind, and that it operates under the same instrumental conditions, what- 

 ever be the primal source of the motor power. And in watching the gradual 

 acquirement of the capacity for different kinds of movement, during the periods 

 of Infancy and Childhood in the Human subject, we find everything to confirm 

 this conclusion. For it becomes obvious that the acquirement of Voluntary 

 power over the movements of the limbs is just as gradual as it is over the 

 direction of the thoughts ( 839) ; all the activity of the body, as well as of the 

 mind, being in the first instance automatic, and the Will progressively extending 

 its domination over the former, as over the latter, until it brings under its control 

 all those muscular movements which are not immediately required for the con- 

 servation of the body, and turns them to its own uses. 1 



2. Of the Symmetry and Harmony of Muscular Movements. 



915. It might have been not unreasonably supposed, d priori, that those 

 muscles would have been most readily put into simultaneous contraction which 

 correspond to each other on the two sides of the body; in other words, that 

 symmetrical movements would be those most readily performed. Such, however, 

 is by no means the case ; for in many of our most familiar actions, we consen- 



1 The aptitude which is acquired by practice, for the performance of certain actions that 

 were at first accomplished with difficulty, seems to result as much from a change which the 

 continual repetition of them occasions in the Muscle, as in the habit which the Nervous 

 system acquires of exciting their performance. Thus, almost every person learning to 

 play on a musical instrument finds a difficulty in causing the two shorter fingers to move 

 independently of each other and of the rest ; this is particularly the case in regard to 

 the ring-finger. Any one may satisfy himself of the difficulty, by laying the palm of the 

 hand flat on a table, and raising one finger after the other, when it will be found, that the 

 ring-finger can scarcely be lifted without disturbing the rest evidently from the difficulty 

 of detaching the action of that portion of the extensor communis digitorum, by which the 

 movement is produced, from that of the remainder of the muscle. Yet to the practiced 

 musician, the command of the Will over all the fingers becomes nearly alike ; and it can 

 scarcely be doubted that some change in the structure of the muscle, or a new develop- 

 ment of its nerve-fibres, takes place, which favors the isolated operation of its several 

 divisions. 



