Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTEACTILE TISSUES 103 A similar curve is obtained if the muscle be stimulated directly. In all such graphic records we should have also— 1. A 117)16 record.—This is furnished by means of a small electro-magnet, armed with a pointed lever writing on the smoked surface. This electro-magnet (time marker or signal) is made to vibrate 100 times a second (more or less as may be required) by putting it in a circuit which is made and broken 100 times a second by means of a tuning-fork vibrating at
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTEACTILE TISSUES 103 A similar curve is obtained if the muscle be stimulated directly. In all such graphic records we should have also— 1. A 117)16 record.—This is furnished by means of a small electro-magnet, armed with a pointed lever writing on the smoked surface. This electro-magnet (time marker or signal) is made to vibrate 100 times a second (more or less as may be required) by putting it in a circuit which is made and broken 100 times a second by means of a tuning-fork vibrating at that rate. The tmiing-fork is maintained in vibration in the same way as the Wagner's hammer of an induction coil. 2. A record of the exact point at which the nerve or muscle is stimulated.—This may be obtained in two ways: a. When using the pendulum or trigger myograph, in Fig. 38. Curve of single muscle-twitch taken on a rapidly moving surface (pendulum myograph) (from Yeo). both of I which the recording surface is a smoked Hat surface on a glass plate, this latter is so arranged that it knocks over a key as it shoots across, and so breaks the primary circuit and excites the nerve or muscle of the preparation. As we know the exact pomt that the plate reaches when it knocks over the key, we can mark on the contraction curve the exact moment at which stimulation took place. h. If we wish to make and break the primary circuit at will by means of a key, a small electro-magnetic signal, inter- posed in the circuit, is arranged to write on the revolving drum, and so mark the point of stimulation. In the figure (Fig. 38) the upper line is the curve drawn by the lever of the muscle as it contracts ; the small upright line shows the point at which the muscle was stimulated ;
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