. Electro-physiology. Electrophysiology. 404 ELECTRO-PHYSIOLOGY CHAP. current of action in the spontaneously beating frog's ventricle. As may be seen, the first phase of the action current begins percep- tibly earlier than the contraction; the negativity of the former (depression' of the meniscus), corresponding with the maximum between base and apex, is reached long before the maxi- mum of contraction, upon which a reversed current ensues as the second phase, when apex becomes negative to base. In Fig. 131, (t) is the time in -^ sec. The capillary electrometer is so connected with the ba
. Electro-physiology. Electrophysiology. 404 ELECTRO-PHYSIOLOGY CHAP. current of action in the spontaneously beating frog's ventricle. As may be seen, the first phase of the action current begins percep- tibly earlier than the contraction; the negativity of the former (depression' of the meniscus), corresponding with the maximum between base and apex, is reached long before the maxi- mum of contraction, upon which a reversed current ensues as the second phase, when apex becomes negative to base. In Fig. 131, (t) is the time in -^ sec. The capillary electrometer is so connected with the base and apex of the ventricle, that the effect is downwards, when base is negative to apex. Cardiac response in the tortoise, and, as shown by A. D. Waller and Eeid (39), in warm-blooded (mammalian) animals, is. Kni. 131.—Curve of contraction (h) and action current (c) of spontaneously beating Frog's heart. (A. D. Waller.) also analogous with that of the frog. With artificial excitation of the excised and already quiescent ventricle, the proximal electrode is found to be at first negative, and immediately after positive, to the distal electrode, and a diphasic variation is thus produced, in consequence of the two phasic action currents, similar in all respects to that of the frog's heart. Owing, however, to the much greater velocity of excitation in the heart of warm - blooded animals, and the abbreviated period of contraction, the two phases merge into each other, as in striated skeletal muscle. Fig. 132, which is a photogram of the movements of the capillary electrometer with a normally beating and artificially excited mammalian heart, shows plainly that each phase corresponds with a simple variation, in the sense of a single excitatory wave. The capillary electrometer also shows a normal. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfec
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