But while the legs have been so actively engaged, there are other parts which have not been idle, so that the same work brings other strength as well. In every step taken, and especially every vigorous one, as in fast walking or in running, the muscles at the sides of the waist have been all the time at work, a prominent duty of theirs being to aid in holding the body erect. Notice a man weak just here, and see his body sway a little from side to side as he walks, seeming to give at the waist. Were such a one to practise daily hopping straight ahead, on one foot, and then on the other, until he could by-and-by so cover half a mile without fatigue, he would find his swaying propensity fast disappearing; and if he has been troubled with a feeble or unshapely waist, that also will have gradually changed, until at the end it has become firm and well-set. Take the long balancing-pole of the tight-rope walker, and try to walk a rope awhile, or try the more simple expedient of walking on the railroad rail, and these muscles are at once uncommonly busy. Notice the professional tight-rope man, and see how strong he is here, especially when to the weight of his own body he adds another, as did Farini when he carried a man on his shoulders across the Niagara River; or as the Eastern porter, with his huge weight of luggage; or the carrier at the meat-market, who shoulders a whole side or more of beef and marches off with it. These men soon get great and unusual power in these side muscles. Wrestling also, whether Cornish or Græco-Roman, or indeed almost any sort, tells directly and severely here. If one prefers to use apparatus made specially, the opposite cut shows a simple device of Dr. Sargent's, which he made purposely to bring up and strengthen these muscles. Standing in front of it, with head and neck erect and chest out, and grasping the ends of the bar A A', the operator simply turns it, first well up to the right, then to the left, and then repeats the movements until he has enough. As he turns, the rubber straps B B stretch more and more, of course getting stiffer the farther the bar is turned. It would scarcely be possible to hit upon a better appliance for improving these valuable side muscles, and yet without fear of overdoing them. [Illustration: Fig. 5. Appliance for developing the Sides of the Waist.] _The Abdominal Muscles._