Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 The contractile tissues 105 which only acts for a short space, gives the frame and the glass plate a rapid horizontal motion; and the momentum carries the glass plate through the rest of the distance, till stopped by the buffers. The velocity during this time is nearly constant, as the friction of the guides is small. Two keys are knocked over by pins on the frame and break electric circuits. The relative positions at which the circuits are broken can be altered by a con- venient adjustment. A t
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 The contractile tissues 105 which only acts for a short space, gives the frame and the glass plate a rapid horizontal motion; and the momentum carries the glass plate through the rest of the distance, till stopped by the buffers. The velocity during this time is nearly constant, as the friction of the guides is small. Two keys are knocked over by pins on the frame and break electric circuits. The relative positions at which the circuits are broken can be altered by a con- venient adjustment. A tuning-fork vibrating about 100 per second fixed to the base of the instrument marks the time; its prongs are sprung apart by a block between their ends, and the same action which releases the glass plate also frees the fork by removing the block and allows it to vibrate; a writing style then draws a sinuous line on the smoked surface of the moving glass plate. A muscle lever with a scale-pan attached also forms part of the nstrument.'' Fig. 40. (T^ Diagram of spring myograph, or ' shooter.' It will be seen that a simple muscular contraction or twitch, such as we have in Fig. 38, produced by a momentary stimulus, consists of three main phases : 1. A phase during which no apparent change takes place in the muscle, or at any rate none which gives rise to any movement of the lever. This is called the latent period. 2. A phase of shortening, or contraction. 3. A phase of relaxation, or return to the original length. The small curves seen after the main curve are due to elastic vibrations of the lever, and do not indicate any changes occurring in the muscle itself. From the time-marking below the tracing, we see that the latent period occupies about ' From Catalogue of Camb. Sci. Inst. Co.
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