double; doubled &c v.; bicipital^, bicephalous^, bidental^, bilabiate, bivalve, bivalvular^, bifold^, biform^, bilateral; bifarious^, bifacial^; twofold, two-sided; disomatous^; duplex; double-faced, double-headed; twin, duplicate, ingeminate^; second.

many sided; multilateral, bilateral, trilateral, quadrilateral.

Symmetry N. symmetry, shapeliness, finish; beauty &c 845; proportion, eurythmy^, uniformity, parallelism; bilateral symmetry, trilateral symmetry, multilateral symmetry; centrality &c 222.

The contraction may be bilateral when affecting both heels of the same foot and extending to the quarters, or unilateral when the inside or outside heel only is affected.

A further useful expansion shoe is that of Hartmann's (Fig. 76), in that it may be adapted for either unilateral or bilateral contraction.

When the contraction is bilateral, the saw-cuts, one or more in number, are placed on each side of the toe-clip.

Various modes of repetitionradical, bilateral, etc.were all probably suggested by some natural arrangement observed in flowers, leaves, etc.

Of these different arrangements it is curious to note that the bilateral is more characteristic of the higher forms of nature and the radiating of the lower.

With them is introduced that character of bilateral symmetry, or division of parts on either side of a longitudinal axis, that prevails throughout the Animal Kingdom, with the exception of the Radiates.

The lowest class of Mollusks has been named Acephala, to signify the absence of any distinct head; for though their whole organization is based upon the principle of bilateral symmetry, it is nevertheless very difficult to determine which is the right side and which the left in these animals, because there is so little prominence in the two ends of the body that the anterior and posterior extremities are hardly to be distinguished.

A cut across an animal of this class will show us better the bilateral arrangement of the parts.