912 OP MUSCULAR MOVEMENTS. 



taneously exert different muscles on the two sides of the body. Thus, in ordi- 

 nary walking, we advance one leg whilst we push backwards (so as to urge the 

 body forwards) with the other; and in the swinging of the arms, which is in most 

 persons a natural part of this mode of locomotion, the arms of the two sides 

 move forwards and backwards alternately, and the arm of either side is advanced, 

 not with the leg of its own side, but with that of the opposite side any other 

 combination being felt as unnatural, and being only performed by a conscious 

 effort. Now it is plain that this grouping of the muscular movements arises 

 out of its felt conformity to the end in view, and that it is regulated by the 

 guiding sensations which indicate to us the progression and balance of the body. 

 The infant, in learning to walk, is prompted by an instinctive tendency to put 

 one foot before the other, as may be noticed at a very early period, when it is 

 first held so as to feel the ground with its feet; and in attempting to balance 

 itself when first left to stand alone, it moves its arms with a like intuitive 

 impulse, not based upon experience. All that experience does, in either case, 

 is to give that precise adjustment to the muscular action, which makes it per- 

 fectly conformable to the indications afforded by the muscular sensations. Thus, 

 if we advance each arm with its corresponding leg, we feel that the balance of 

 the body is not nearly so readily maintained, as it is when we advance the arm 

 with the leg of the opposite side; and thus, without any design or voluntary de- 

 termination on our own parts, the former comes to be our settled habit of action. 

 This kind of adjustment, in the case before us, is by no means limited to the 

 muscles of the limbs; for there is scarcely any muscle of the trunk or head that 

 is not exerted with some degree of consentaneous energy, however unconsciously 

 to ourselves, in the act of walking. The difficulty which would attend the 

 voluntary harmonization of all these separate actions is remarkably evinced by 

 the fact, that no mechanist, however ingenious, has ever succeeded in construct- 

 ing an automaton that should walk like Man; the alternate shifting of the centre 

 of gravity from one side to the other, upon so small a base as the human foot 

 affords, simultaneously with its movement in advance, constituting the great 

 difficulty of biped progression. But all this adjustment is effected in our own 

 organisms, for us, rather than by us ; the act of harmonization, when once fully 

 mastered, being attended with no effort to ourselves, but the whole series of 

 complex movements being performed in obedience to the simple determination 

 to walk, under the automatic guidance of the senses, which instantly reveal to 

 us any imperfection in the performance. The same view extends itself readily 

 to other combinations of dissimilar and non-symmetrical movements, which are 

 less natural to Man, but which may be readily acquired artificially if they all 

 harmonize in a common purpose, and are under the guidance of the same set of 

 sensations. Thus, the performer on the organ uses his two hands to execute 

 different movements (in very different positions, it may be) on the "manual" 

 keys, one of his feet may be on the "swell" pedal, and the other may be en- 

 gaged in playing on the "pedal" keys; but all these diverse actions are har- 

 monized by their relation to the same set of auditory sensations ; and if the result 

 be not that which the performer anticipated, an immediate correction is made. 



916. It would be easy to multiply instances of the same kind, all illustrative 

 of the general principle, that the facility with which we voluntarily combine 

 different movements is chiefly determined, not by their symmetrical character, 

 but by their conformableness to a common end, and by the harmony of their guid- 

 ing sensations with reference to that end; 1 but it will be desirable to dwell par- 



1 Two simple examples, however, may be cited, of the difficulty which attends the simul- 

 taneous performance of movements that are not harmonious. If we attempt to elevate one 

 eyelid whilst we are depressing the other, we find that a considerable effort is required to 

 accomplish the action, although the elevation or depression of both eyelids together is 

 performed with so little effort that we are scarcely conscious of it ; and the difficulty is in- 



