. A system of anatomy for the use of students of medicine (Volume 1). at could be done to increase the power, with-out impairing the symmetry of the body, or diminishing the celerityof its movements, has been accomplished in endowing the mus-cles, with an extraordinary force of contraction, at least ten foldas great as the student would at first suppose it. The musclesare nearly all levers of the third order. —The force with which a muscle contracts, depends upon itsvolume and the energy of the will, as well as some other circum-stances. But the effect produced by the contraction will dependin
. A system of anatomy for the use of students of medicine (Volume 1). at could be done to increase the power, with-out impairing the symmetry of the body, or diminishing the celerityof its movements, has been accomplished in endowing the mus-cles, with an extraordinary force of contraction, at least ten foldas great as the student would at first suppose it. The musclesare nearly all levers of the third order. —The force with which a muscle contracts, depends upon itsvolume and the energy of the will, as well as some other circum-stances. But the effect produced by the contraction will dependin a great measure upon the manner in which it is inserted uponthe bone on which it acts. —Thus, all things being the same, the effect of the contractionwill be the greater, in proportion asthe muscle is less obliquely con-nected with the bone. Thus of themuscle m, figure 14, the force ofwhich we suppose equal to 10, is fixed perpendicularly to the bone /,the extremity of which a, is mova-ble upon the fulcrum point r, it willhave to overcome only the weight * 23*. 270 FORCE OF MUSCULAR CONTRACTION. of the bone, and will carry it from the position a b, into thedirection of the line a c. But if this muscle acted obliquely uponthe bone in the direction of the line n b, it would then tend tocarry it in the direction of the line b n, and consequently to forceit against the fixed articular surface r. This latter being a fixedsurface, the bone can only turn upon the point r, as upon a pivot,and the contraction of the muscle n, having the same force asthe muscle m, would only be able to carry the bone in the direc-tion a d, and would require a force equal to 40, or four timesthat of m, to raise it in the direction of the line a c.—In the animal economy the muscles are inserted most usually,very obliquely, and consequently in a manner little favourable tothe intensity of the result of their contraction. There is never-theless a very happy contrivance, which tends to diminish theobli
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