. Elements of human physiology. Physiology. 1'2G PHYSIOLOGY is still contracted while the base is relaxed, and the apex is therefore negative to the base. This terminal negativity of the apex is shown on the photograph by the excursion of the column of mercury away from the point of the capillary at (4). The only difference between the electrical changes in this case and in that of voluntary muscle is that in the latter all processes are very much quicker, so that as a rule the point (a) (Fig. 56) has ceased to be negative before the Fm. â 11'' .-aci(I Diagram of capillary electrometer. H
. Elements of human physiology. Physiology. 1'2G PHYSIOLOGY is still contracted while the base is relaxed, and the apex is therefore negative to the base. This terminal negativity of the apex is shown on the photograph by the excursion of the column of mercury away from the point of the capillary at (4). The only difference between the electrical changes in this case and in that of voluntary muscle is that in the latter all processes are very much quicker, so that as a rule the point (a) (Fig. 56) has ceased to be negative before the Fm. â 11'' .-aci(I Diagram of capillary electrometer. Hg., Mercury. The two terminals are represented as leading off two points at the base and apex of a frog's heart, a b. negativity of (b) has attained its full height, and there is thus no prolonged equipotential stage. Although in the case of the slowly contracting ventricle of the tortoise, the record obtained of the electrical changes accompanying its contraction by means of the capillary electrometer shows with great clearness the diphasic nature of the variation, and therefore the wave character of the electrical change, considerable dilliculty is at first experienced when we attempt to inter- pret in the same way the electrometer record of the electrical response of voluntary muscle. In this case the electrical change at any spot only lasts about ^7^5 of a second, and there is not a prolonged equij)otential period, as in the case of the heart. The diphasic nature of the variation is however obvious, if we compare the electrometer record of an intact and therefore currentless muscle with that of the change produced by a single stimulus in a muscle in which one of the leading-off points has been injured, so as to give rise to a demar- cation current. The two curves are given in Fig. .59, the upper shadowy tracing being that obtained from the injured muscle. It will be seen that the. Please note that these images are extracted from scanned page images that may have been digit
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