Response in the Living and Non-living (Google eBook)

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Longmans, Green, and Company, 1902 - Electrophysiology - 199 pages
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Page 97 - ... 01 of this value. The intensity of the response, however, does not depend on the chemical activity of the substance, for the electromotive variation in the relatively chemically-inactive tin, and even gold, is greater than that of zinc. Again, the sign of response in silver, positive or negative, defends on its molecular condition.* 2.
Page 103 - Mechanical responses in muscle. again is modified by any influence which affects the molecular condition. That the excitatory state persists for a time even on the cessation of stimulus can be independently shown by keeping the galvanometer circuit open during the application of stimulus, and completing it at various short intervals after the cessation, when a persisting electrical effect, diminishing rapidly with time, will be apparent...
Page 167 - ... is in the first place increased, then diminished; during the continuance of light it is still slowly diminished to a point where it remains constant; and on the removal of light, there is a sudden increase of the electromotive power nearly up to its original position.
Page 175 - ... that I came upon the curious fact that the two eyes do not see equally well at a given instant, but take up, as it were, the work of seeing, and then (relatively speaking) resting, alternately. There is thus a relative retardation of half a period as regards maximum sensation in the two retinas. This may be seen, by means of a stereoscope, carrying, instead of stereophotographs, incised plates through which we look at light. The design consists of two slanting cuts at a suitable distance from...
Page 190 - The investigations which have just been described may possibly carry us one step further, proving to us that these things are determined, not by the play of an unknowable and arbitrary vital force, but by the working of laws that know no change, acting equally and uniformly throughout the organic and the inorganic worlds.
Page 11 - negative variation" of current of rest. Index connected with galvanometer needle records curve on travelling paper (in practice, moving galvanometer spot of light traces curve on photographic plate). Rising part of curve shows effect of stimulus; descending part, recovery. on such surface being in a similar molecular condition, their electrical level or potential will be the same. They are iso-electric. No current will be exhibited by the indicating galvanometer when two non-polarisable electrodes*...
Page 95 - Modifications of experimental arrangement to show electric response in metals. quick torsional vibration round the vertical wire, as axis, by means of the handle. As the wire A is separate from B, disturbance of one will not affect the other. Vibration of A produces a current in one direction, vibration of B in the opposite direction. Thus wo have means of verifyingevery experiment by obtaining corroborative and reversal effects.
Page 94 - Fig. 9. Two pieces, from the same specimen of wire, are clamped separately at their lower ends by means of ebonite screws, in an L-shaped piece of ebonite. The wires are fixed at their upper ends to two electrodes (leading to the galvanometer), and kept moderately and uniformly stretched by spiral springs. The handle, by which a torsional vibration is imparted to the wire, may be slipped over either electrode. The amplitude of vibration is measured by means of a graduated circle, not shown in the...
Page 13 - On now stimulating the wire, a diminution of this current of injury, or negative variation, will be produced. with its terminal organs, gives sign of life by means of muscle, which by direct or reflex path is set in motion when the nerve-trunk is stimulated. But such nerve, separated from its natural termini, isolated from the rest of the organism, gives no sign of life when excited, either in the shape of chemical or of thermic changes, and it is only by means of an electrical change that we can...
Page 10 - The excitatory state evoked by stimulus manifests itself in nerve fibre by electromotive changes, and as far as our knowledge goes, by these only. . . . The conception of such an excitable living tissue as nerve implies that of a molecular state which is in stable equilibrium. This equilibrium can be readily upset by an external agency, the stimulus, but the term

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