These symptoms are in all probability dependent upon, or are at least coincident with, a hyperæmia of the nerves and spinal cord, and, if persisted in for a long time without proper intervals of rest must sooner or later interfere with the healthy condition of the spinal cord, as well as of the nerves and muscles of the hand and arm.
Poore, while considering the symptoms of fatigue as in large part peripheral in origin, readily admits that they must generally be accompanied by central changes.
The manner of writing and of holding the pen is of considerable influence in the causation of this trouble. Practically, the fluent writer is more apt to contract this affection than he who writes badly, for the latter seldom obtains a position where steady copying is to be done; theoretically the reverse is true if the amount of work in the two cases is the same.
When the pen-holder is allowed to drop below the head of the first metacarpal bone the movements of the fingers are restricted; the middle and fore finger upon one side of the holder and the thumb on the other act upon the principle of the toggle-joint, so well known in mechanics, and, as the pen-holder is drawn backward to make a stroke, bind the distal phalanges tightly against the holder: this in a short time causes fatigue and awkwardness in writing; but if the holder is made to cross the proximal extremity of the first phalanx of the fore finger the toggle-joint movement is destroyed.
These remarks apply of necessity more strongly to the finger movements than to the conjoined finger-and-arm movement.
Writing with a pencil is not as liable to bring on fatigue and nervous trouble as pen-writing, this being mainly owing to the fact that with the former no particular angle is required to be maintained between the point and the paper; there is therefore less effort at poising, as the pencil may be rotated at pleasure, while with the pen one angle has to be maintained. The same remarks should apply to the fluid pencils (stylographic and Mackinnon pens) now so universally used; in fact, they have been considered by Putnam5 as much easier to write with than the pencil, as less weight need be applied upon the tip in order to write.
5 J. J. Putnam, M.D., “A New Adjuvant in the Treatment of Writers' Palsy,” Boston Med. and Surg. Journ., vol. ci. p. 320, 1879.
The idea that these troubles of writers were due to using steel pens, as once thought, is manifestly without foundation, as the affection was recognized before the time of the introduction of steel pens, which was from 1800 to 1820.
Fine sharp pens are, however, more productive of evil than composition pens or those with a broad soft nib, as they do not move as easily over the paper, and therefore introduce a difficulty, although a slight one, in the act of writing. The theory that the chemical action between the ink and the metallic pens, and the friction of the pen on the paper, generate sufficient electricity to affect the fingers through the medium of the metallic portion of the pen-holder is too preposterous to mention, except to show what curious reasons are given in attempting to explain obscure and difficult subjects.
The next occupation which very frequently gives rise to these affections is telegraphy.