The Bones of the Right Wing of a Duck

“Fig 27. - Bones of the right wing of a duck, Clangula islandica, A, shoulder, omos; B, elbow, ancon; C, wrist, carpus; D, end of principal finger; E, end of hand proper, metacarpus. AB, upper arm, brachium; BC, fore-arm, antibrachium; CD, whole hand or pinion, manus; composed of CE, hand proper or metacarpus, excepting d2; ED, or d2, d3, d4, fingers, digits, digiti, h, humerus; rd, radius; ul, ulna; sc, outer carpal, scapholunare or radiale; cu, inner carpal, cuneiforme or ulnare; these two composing wrist or carpus. mc, the compound hand-bone or metcarpus, composed of three metacarpal bones, bearing as many digits - the outer digit seated upon a protuberance at the head of the metacarpal, the other two situated at the end of the bone. d2, the outer or radial digit, commonly called the thumb or pollex, composed or two phalanges; d3, the middle digit, of two phalanges; d4, the inner or ulnar digit, of one phalanx d2 is the seat of the feathers of the bastard wing or alula. D to C (whole pinion), seat of the flight feathers called primaries; C to B (fore-arm), seat of the secondaries; at B and above it in direction of A, seat of tertiaries proper; below A, in direction of B, seat of scapularies (upon pteryla humeralis), often called tertiaries. The wing shown half-spread: complete extension would bring A B C D into a right line; in complete folding C goes to A, and D to B; all these motions nearly in the plane of the paper. The elbow-joint and wrist are such perfect hinges, that, in opening or closing the wing, C cannot sink below the paper, nor D fly up above the paper, as would otherwise be the effect of the pressure of the air upon the flight-feathers. Observe also rd and ul are two rods connecting B and C; the construction of their joining at B and C, and with each other, is such, that they can slide lengthwise a little upon each other. Now when the point C, revolving about B, approaches A in the arc of a circle, rd pushes on sc, while ul pulls back cu; the motion is transmitted to D, and makes this point approach B. conversely, in opening the wing, rd pulls back sc, and ul pushes on cu, making D recede from B. In other words, the angle A B C cannot be increased or diminished without similarly increasing or diminishing the angle B C D; so that no part of the wing can be opened or shut without automatically opening or shutting the rest...” Elliot Coues, 1884

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