Oliver-Sharpey lectures on the nature of flutter and fibrillation of the auricle : delivered before the Royal College of Physicians of London, April 14th, 1921 / by Thomas Lewis.

  • Thomas Lewis
Date:
1921
Catalogue details

Licence: Public Domain Mark

Credit: Oliver-Sharpey lectures on the nature of flutter and fibrillation of the auricle : delivered before the Royal College of Physicians of London, April 14th, 1921 / by Thomas Lewis. Source: Wellcome Collection.

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    SomE NorMAL FEATURES OF THE CONTRACTION PROCESS. Let me first briefly describe the relevant events when normal heart muscle contracts in response to a natural or artificial stimulus. The first event of which we possess knowledge is that it passes into what is termed the state of excitation. By this we mean that the muscle develops a charge, just as a battery develops a charge, and that cur- rents flow through it and the surrounding tissues. The charge is such that the active muscle becomes relatively negative to that which is still inactive, in the sense that the zinc terminal of a copper-zinc battery is negative to the copper. These electrical changes, associated with muscular activity, are of sufficient magnitude to be recorded by means of sensitive instruments, and they yield the pictures now spoken of as electrocardiograms. The elec- trical change in the muscie is the immediate precursor of contraction :* first the muscle becomes excited (or charged), secondly it contracts. The two events are separated in the mammalian auricle by a small time interval of three-hundredths of a second or less. Now the process of excitation is not simultaneous in all parts of the muscle; it begins at the point first stimulated and spreads from this point. Stimulate a point in the centre of a sheet of muscle and the wave spreads concen- trically, as does the ripple on the surface of a pond into which a pebble is thrown. It is conducted from one muscle element to the next as a wave, which is termed the wave of excitation. Similarly with the contraction pro- cess itself; this also spreads as a wave which accurately follows the course travelled by the wave of excitation. It may be likened to the second ripple on the pond. For our * That the Miaeteiu change precedes the contraction is at the moment the accepted view, though the interval is acknowledged to be very short.
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