SYMMETRY AND HARMONY OF MUSCULAR MOVEMENTS. 833 



partly upon direct muscular effort: the longer the leg, the slower will be the 

 oscillation ; but by planting the foot on the ground when it has only passed 

 through one-half of its natural oscillation, the succession of steps, and con- 

 sequently the rapidity of progress, can be materially increased, without much 

 effort. In very quick walking almost every muscle in the body is brought 

 into play ; the trunk is considerably inclined forwards, partly for the purpose 

 of resisting and compensating for atmospheric pressure, but chiefly to enable 

 the hip-joints to be carried low, thus increasing the extent of ground which 

 can be covered by each step, whilst at the same time the number of steps is 

 greatly increased by muscular effort; the period during which both feet are 

 resting on the ground together being considerably shortened. In an experi- 

 ment made by Mr. Vasey, the length of whose leg was thirty-four inches, in 

 walking at the rate of four miles an hour, 2000 steps were made every fifteen 

 minutes ; the length of each step must therefore have been 2.64 feet, and the 

 time of each step 0.45 second. M. Carlet has shown that the muscular effort 

 in walking, as indicated by the backward push, supposing the weight of the 

 individual to be about 150 pounds, does not surpass 45 pounds additional, 

 though it is much greater in leaping and running. Quick walking passes 

 by insensible gradations into running, the period in which the body rests 

 upon both feet becoming shorter and shorter, until at length there is a 

 period between successive steps, during which the body moves forward un- 

 supported by either foot. According to Weber, the vertical undulations of 

 the trunk in running vary from |ths to 4ths of an inch, the duration of the 

 step from ^th to |th of a second, of which time the body swings unsupported 

 in the air T 'jjth of a second, the time of descent being yVth of a second. In 

 leaping, the extensor muscles are brought into extremely vigorous action, 

 and the act may be accomplished either by the alternative or the simul- 

 taneous action of the legs, as seen in the "hop, step, and jump" of children. 

 The essential difference in leaping and running is, that in leaping the body 

 is raised so high from the ground, and for so long a period, that the leg or 

 legs have time to complete their full arc of oscillation, and consequently 

 cover the utmost space of ground possible. The extent of the leap is of 

 course dependent upon the muscular energy of the individual. 1 



682. Now it is plain that the grouping of the muscular movements in 

 these different instances 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 perfectly 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 as 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 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 un- 



1 The subject of the locomotion of Man has been particularly investigated by the 

 Profs. Weber, whose work entitled Mechanik der menschlich. Gehwerkzeuge (Got- 

 tingen, 1836) has been translated in Jourdan's Encyclopedic Anatomique, torn. ii. 

 See also the Art. Motion, by Mr. J. Bishop, in Cyclop, of Anat. and Physiol./vol. iii. 



