Some medico-legal cases under state and national laws / by B. Joy Jeffries.

  • Jeffries, B. Joy (Benjamin Joy), 1833-1915.
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Some medico-legal cases under state and national laws / by B. Joy Jeffries. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    7/22 (page 229)
    the eye immediately and may now be still more accurately measured. The primary rhythm I obtained with the aid of Maelzel’s metronome. By shifting the weight on the pendulum we can regulate the number of strokes at will, and by inclining the instrument, we can make the strokes alternately unequal. These strokes themselves are not, however, to be used, for the moments of origin are not to be registered; but I attached to the pendulum a wire in a horizontal direction, bent the two extremities left and right downwards, and in the vibrations of the pendulum caused these bent extremities to dip into mercurial troughs, whereby a galvanic current was at the same time closed. To insure the regular action of the instrument, it now appeared to be even better not to incline it, but to produce the alternate difference merely by altering the length of the wire, and by placing the one mercurial trough higher than the other. Now on each closing of the current, the arm of a marker was attracted by an electro-magnet, in a distant room, where the strokes of the metronome could not be heard, and the moments of attraction, with alternately greater and shorter pauses, were here registered on the revolving cylinder of the kymographion. As we heard in the strokes of the markers upon the magnet the registered rhythm, we had only to imitate this with the hand, in the mode above described—by striking, in fact, upon a marker, which registered its movements directly above those produced by the magnet. In this manner we obtain figures like the subjoined : Fig. 3. The tracing M is the primary rhythm, derived from the metronome; J is the imitated rhythm. In both tracings three whole periods are to be seen: III represents a, II F is A, &c,; at a the markers descend, at d they are set free and ascend by their elasticity, at c they descend anew to rise again at d, and at a' a second period begins. It here appears distinctly, that in the imitated rhythm I occurs some- what too late and II often rather too early, so that « is reproduced too small and A too great. The same occurs when, as in fig. 4, Fig. 4.