623 Sûˋdillot, De lãinfluence des fonctions sur la structure et la forme des organes; C. R. LIX, p. 539, 1864; cf. LX, p. 97, 1865, LXVIII. p. 1444. 1869.
624 E.g. (1) the head, nodding backwards and forwards on a fulcrum, represented by the atlas vertebra, lying between the weight and the power; (2) the foot, raising on tip-toe the weight of the body against the fulcrum of the ground, where the weight is between the fulcrum and the power, the latter being represented by the tendo Achillis; (3) the arm, lifting a weight in the hand, with the power (i.e. the biceps muscle) between the fulcrum and the weight. (The second case, by the way, has been much disputed; cf. Haycraft in SchûÊferãs Textbook of Physiology, p. 251, 1900.)
625 Our problem is analogous to Dr Thomas Youngãs problem of the best disposition of the timbers in a wooden ship (Phil. Trans. 1814, p. 303). He was not long of finding that the forces which may act upon the fabric are very numerous and very variable, and that the best mode of resisting them, or best structural arrangement for ultimate strength, becomes an immensely complicated problem.
626 In like manner, Clerk Maxwell could not help employing the term ãskeletonã in defining the mathôÙeôÙmatôÙiôÙcal conception of a ãframe,ã constituted by points and their interconnecting lines: in studying the equiôÙlibôÙrium of which, we consider its different points as mutually acting on each other with forces whose directions are those of the lines joining each pair of points. Hence (says Maxwell), ãin order to exhibit the mechanical action of the frame in the most elementary manner, we may draw it as a skeleton, in which the different points are joined by straight lines, and we may indicate by numbers attached to these lines the tensions or compressions in the corôÙreôÙsponôÙding pieces of the frameã (Trans. R. S. E. XXVI, p. 1, 1870). It follows that the diagram so constructed represents a ãdiagram of forces,ã in this limited sense that it is geometrical as regards the position and direction of the forces, but arithmetical as regards their magnitude. It is to just such a diagram that the animalãs skeleton tends to apôÙproxôÙiôÙmate.