A system of practical medicine. By American authors. Vol. 5

by Unknown

¹⁰ Wm. A. Hammond, M.D., Dis. Nervous System, 6th ed., New York, p. 789.

¹¹ J. B. Abernethy, Commercial and Railway Telegraphy, Cleveland, Ohio, 1883, 2d ed.

Operators are very loath to confess that they are suffering from loss of grip, as they have termed it, for then they are considered as less efficient than formerly, and may be asked to resign in favor of one not affected, or be lowered in their salary—a point of great moment, as telegraphy is their means of support. This accounts for the apparent small number of the cases.

In telegraphing, the knob of the key, a circular disc of hard rubber more than one inch in diameter, and placed about one and a half inches above the level of the table, is grasped, as a rule, between the thumb and middle finger, with the tip of the index finger resting on top, the position being quite analogous to the method of pen-prehension, the strain, although much less, falling on the same muscles, but as all lateral movements of the key are impossible, the muscles employed in poising are not brought into play as in writing. The arm is either allowed to rest upon the table, upon the flexor mass of muscles of the forearm near the elbow as a kind of movable fulcrum, or is held with the forearm parallel to the table and a short distance above it.

The movements of telegraphing are made by the alternate action of the triceps, which depresses the wrist by extending the forearm, assisted by the flexor carpi radialis, flexor carpi ulnaris, flexor sublimis, and flexor profundus digitorum on the one hand, and the biceps and supinator longus, which elevate the wrist by flexing the forearm, assisted by the extensor carpi radialis longior, extensor carpi radialis brevior, extensor carpi ulnaris, and extensor communis digitorum on the other.

The movement of the key-knob, being about the one-twenty-fifth of an inch, is so slight that it may be entirely ignored, so that with the fingers upon the key and the forearm resting upon the table near the elbow the motion must be a downward and upward one of the wrist; when, however, the arm is held above the table and parallel to it, the motion is more extended, the shoulder-muscles being used to support the arm.

The wrist is held in a supple manner, and not rigidly, the momentum of the downward movement being used to close the circuit; this, as before stated, is made mainly by the triceps, and is checked by the flexors and supinator longus.

The extensors of the wrist and fingers have a double duty to perform, for, besides assisting in recovering from the downward stroke, they have to support the hand during the whole act of telegraphing, in order to prevent the weight from resting on the key, which would prevent quickness in making and breaking the circuit.

On long circuits, particularly in wet weather, when much electricity escapes from the line, the movements have to be made with much more decision than usual in order to make the signals intelligible at the distant station.

The accompanying diagram shows well the movement of the wrist as above described, the hand and wrist moving into the position of the dotted lines when the downward stroke is made.