The introduction of American artificial legs into this country has not been so revolutionary in its results as it is apparently in France, for we have been accustomed for many years to make the bucket out of a single piece of willow. The alterations in our methods introduced recently from America are essentially the following—
1. The use of a sling which passing over the shoulders is attached to the leg below the knee in such a way as to act as a mechanism for extending the knee.
2. The manufacture of the leg portion out of a single piece of wood.
3. The abolition of the old tendon action for the ankle joint (which resembled the mechanism described on [page 57]) and its replacement by the ankle with movement limited by indiarubber buffers.
4. Covering the wooden part of the limb with a layer of raw hide or parchment, which certainly adds to the strength.
The sole remaining problem in the design of artificial legs appears to be the invention of a knee mechanism which will lock in any degree of flexion when a strain is put upon it, so that the wearer does not necessarily fall when his weight comes upon the limb with the knee flexed. A recent invention, still on its trial, seems to indicate that this problem is not incapable of solution.
In artificial arms the differences between the French and English patterns are greater than in artificial legs. But here again the principles remain the same. In England, also, we have worker's arms and show arms, but the latter tend to be more elaborate than the French patterns, mechanical movements being more developed. For this reason this pattern is usually called, in England, the mechanical arm. Instead of the single cord, looped round the opposite shoulder, and used to open the spring thumb (see [p. 101]), at least three such cords are used, actuated (1) by rounding the back; (2) by expanding the upper part of the chest, and (3) by raising or lowering the shoulder on the side of the amputation. These may be used for various purposes, of which the chief are (1) flexing the artificial elbow; (2) working the elbow lock, and (3) actuating the thumb, fingers or appliances used instead of the hand. The chief other differences in the methods adopted in England are—
1. A smaller enclosure of the shoulder region for purposes of suspension, the limb being held on by a harness of straps. We, in fact, value mobility of the shoulder, and gain it at the expense of stability.
2. The use of various alternative patterns of elbow locks.
3. The appliances used instead of the hand are very different in pattern, although the principles for their construction remain as described here by the authors.