Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTRACTILE TISSUES 127 distinguishing character of a diphasic variation in the rapidly contracting striated muscle consists in the fact that the downstroke of the image of the meniscus is as rapid as the upstroke, whereas the monophasic variation of the injured muscle presents a slow fall produced by the gradual leakage of the charge imparted to the instrument back through the electrodes and muscle. Knowing the constants of the instrument used, it is possible, by measuring the curvature of
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTRACTILE TISSUES 127 distinguishing character of a diphasic variation in the rapidly contracting striated muscle consists in the fact that the downstroke of the image of the meniscus is as rapid as the upstroke, whereas the monophasic variation of the injured muscle presents a slow fall produced by the gradual leakage of the charge imparted to the instrument back through the electrodes and muscle. Knowing the constants of the instrument used, it is possible, by measuring the curvature of this ' spike,' as the record of the diphasic variation is termed, to determine accurately the electromotive force of the action current producing the excursion of the electrometer. An exactly similar curve can be obtained by putting in a current of similar fi'om a battery, first in one direction for t^^-, of a second, and then in a reverse direction for another ^^^ of a second. It must be remembered that a diphasic variation does not mean that one part of a muscle changes from normal in one direction, and then swings back Fig. 59. Superimposed photographs of the electrical variation of the sartorius in response to a single stimulus. (Burdon-Sanderson.) past the normal in another direction, but that a change in one direction at one electrode dies away and is succeeded by a similar change in the same direction, which also dies away, at the second electrode: that is to say, a diphasic variation implies a progression of a wave of electrical change between the leading-off points. It is found that the rate of transmission of this electrical change in muscle is exactly the same as the rate of propagation of the wave of contraction, and amounts at ordinary temperatures to about 3 metres per second. We may now return for a moment to the consideration of the current of rest observed in injured muscle. Hermann considers that muscle (or contractile tissue) becomes negative under
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