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cave extremities of the upper and lower arm pieces was inserted a wooden sphere, bound to the adjacent concavities by a strong spring. The friction between the opposing surfaces was sufficient to lock the arm at any desired angle. With
Fig. 148.-Judge Corley's apparatus for helping the man who has lost both
hands to button his own collar.
the aid of this simple device, the patient within two years became an expert carpenter and, entirely unassisted, was able to do the finest kind of cabinet work. Of course it must be remembered that the artificial hand plays the role of assistant to the sound arm, and the success of the patient in becoming an expert artisan was due in large part to the fact that the major work done by the carpenter is performed by one hand aided to a com paratively slight degree by the other.
Fig. 149.-A 14-year old carpenter's apprentice amputated at the elbow, showing the artificial limb which he himself designed. By inserting a wooden sphere between the concave extremities of the upper and lower arm pieces he could not only flex and extend but supinate and pronate.
Another valuable type of arm is illustrated in Fig. 152.
This device is purely for working purposes, and must be supplemented by another arm which hides the defect. It consists of a broad padded metal ring which fits over the shoulder and is held firmly in place by straps passing around the body. To this ring is attached a second, which, running on ball bearings, has perfect freedom of rotation on the first ring. To the second are attached steel uprights which run parallel with the stump and terminate at the level of the elbow in a circular disc to which various instruments useful to the carpenter can be
attached. The stump is bound firmly to the steel uprights by means of straps, and owing to the ball-bearing joint at the shoulder the wearer has almost the normal range of motion. A little ingenuity in devising the tools to be inserted into the disc enables the amputated to do even the most delicate kind of carpentry work. One tool suffices to grasp the screw of the screw-and-bit; another grasps the nail so that the uninjured hand is free to hammer; another is designed to hold the chisel, etc.
An interesting modification of the working arm suitable for amputations above the elbow, is the utilization of a spring at
Fig. 151.—The carpenter's apprentice already pictured in the preceding figures, at work with the saw. The artificial limb is used to steady the board.
the elbow-joint, which permits a springy motion of distinct value in hammering, filing, etc., work in which absolute fixation at the elbow takes away from the freedom of the stroke. Fig. 154 illucidates the principle of this arm. By fastening screws A and B, the arm can be absolutely fixed at any desired
Fig. 153.—The Biesalski artificial arm for amputations above the elbow. (First model.) This arm was probably the first in which an elbow joint was constructed corresponding to the anatomy of the normal, and the first in which a working arm was combined with an æsthetic means of hiding the defect. The lower arm portion consists of a strong metal tube, into which working implements can be inserted and over which the artificial hand can be placed, when the wearer is through with his day's work.