Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 104 PHYSIOLOGY and the second line is the tracing of the chronograph, every vibration representing -5^ of a second. In the pendulum myograph (Fig. 39) a smoked glass plate is carried on a heavy iron pendulum. At each side the pendulum is armed with a catch, which fits on to other catches at the side of the triangular box, from the apex on which the pendulum is suspended. At its lower part the pendulum carries a projecting piece which can knock over the ' kick-over' key (k), thus breaking a circu
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 104 PHYSIOLOGY and the second line is the tracing of the chronograph, every vibration representing -5^ of a second. In the pendulum myograph (Fig. 39) a smoked glass plate is carried on a heavy iron pendulum. At each side the pendulum is armed with a catch, which fits on to other catches at the side of the triangular box, from the apex on which the pendulum is suspended. At its lower part the pendulum carries a projecting piece which can knock over the ' kick-over' key (k), thus breaking a circuit in which is included the primary coil of an induction coil. The lever attached to the muscle is arranged so as to write lightly on the glass plate, Everything being ready, and the key (k) closed, the pendulum is raised to a, the Fig. 39. Simple form of pendulum myograph. catch (a) is then released, and the pendulum falls at an ever-accelerating rate and then rises again, gradually slowing off until it is caught again at b. As it passes by the key it breaks the circuit. A break induction shock is sent into the muscle or nerve, which contracts, and a curve is obtained similar to that shown in Fig. 38. Since the rate of the pendulum is constantly varying throughout its course, it is necessary to have a tuning-fork, or time- marker actuated electrically by a tuning-fork, writing just below the muscle- lever. In the spring myograph, otherwise known as the trigger or shooter myograph (Fig. 40), a smoked glass plate is also used. ' The frame supporting the glass plate slides on two horizontal steel wires. To make the instrument ready for use, the frame is moved to one side, which compresses a short spring. When the catch holding it. in this position is released by the trigger, the spring
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