Description of an artificial hand / By Sir George Cayley.

  • George Cayley
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: Description of an artificial hand / By Sir George Cayley. Source: Wellcome Collection.

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    be so arranged as to keep a nearly equal tension or pressure to retain the rods B, and K, of the upper and lower arms, in a right line with each other, and to restore them to that, position whenever the elbow joint is bent. By this means, supposing a glass, a spoon, or other matter of light grasp be lifted to the mouth, as before described, it will not then be necessary to take it away from that position with the other hand, as when the friction plate is used, for the reaction of the spring will continue the grasp, as the arm unbends by the downward movement of the stump. One necessary aid to this instrument in all its forms is, to give support to its weight from the neck and shoulder ; which, in the case of George Douseland, is effected by a padded flat iron hook, surrounding a consider¬ able portion of the neck, under the collar of the waistcoat, and passing behind it, so as to terminate on the shoulder, where it is cupped a little, to give it firmness of seat. To this part the upper ring A of fig. 1 is attached by a couple of straps with buckles,—see fig. 5. By this means, the arm is not fatigued by the weight of the apparatus, and the joint F is at all times preserved in the same line of axis as that of the elbow joint, with which it has to move as on a centre common to both. As the hollow ball and socket movement, previously suggested, will require very excellent workmanship to render it efficient, it will be as well here to remark, that with much coarser work the wrist movement may be effected by an external hoop, similar to H, fig. 1, containing a second, that can turn completely round freely within it, but confined from escaping by any of the usual means. The inside of this hoop should be cupped, so as to approach a section of the globular form ; and a third hoop, externally, a similar segment of a globe, but a size smaller, must fit, without much nicety of adjustment, within the second. An axis passing through the centre of both these spherical portions is fixed to the inner one, but turns freely in a collar in the second, the end being flush with its exterior sur¬ face. The ball and socket action, so far as it is used, is here derived from the one turning on an axis within the other, and not from the accurate