Arhythmia of the heart : a physiological and clinical study / by K.F. Wenckebach ; translated by Thos. Snowball.

  • Wenckebach, K. F. (Karl Friedrich), 1864-1940.
Date:
1904
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Licence: In copyright

Credit: Arhythmia of the heart : a physiological and clinical study / by K.F. Wenckebach ; translated by Thos. Snowball. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    tensity is built up in the muscle cells of the%i-eat veins, where a compensatory pause does not occur, this stimulus manifesting itself in rhythmical contractions, as with tetanisation, just because at every systole the heart is at once withdrawn from the action of the stimulus. Kronecker ^'^^ refers to this possibility, but ascribes the property of converting a tetanising into a rhythmical stimulus to the central organs. But in the case of the heart it is not neces- sary to accept the notion of an increased tonus of the central organs causing this make and break, because here the refractory phase of the muscle itself gives a satisfactory explanation ! Now, if it were really the case that the physiological stimulus were a continuous one, that manifested itself in rhythmical contrac- tions by virtue of the alternation of excitability and'non-excitability, the rate at which the heart beats would then be dependent on the relation between the uniform intensity of the stimulus and the excit- ability of the organ, i.e. in fact, on the excitability alone. This view is advocated by H. E. Hering (^^ p. 579). Muskens^^^^ advanced the theory that the moment at which the stimulus becomes effective depends exclusively on the power of the heart to conduct the stimulus onwards. In opposition to this, Engelmann put forward the view that the contraction-stimulus is really formed continuously, but is destroyed at every beat by the contraction, and must then be formed again anew, and this view he has managed to support by the proof that the formation of the stimulus is, within wide limits, independent of the excitability and conduction-power of the heart. The process may, therefore, be presented to our minds in the following way:—Stimulus-matter is being continually formed in the heart-muscle cells, most energetically in those situated at the venous end of the heart. When it grows to such a strength as to set up a contraction, the molecular explosion that occurs at the systole not only abolishes the excitability and contractility for a short time, but also destroys the .stimulus-matter itself. After the systole, therefore, it must be built up again anew to the point of requisite strength, and the time that elapses ceteris parihus until this point is reached is just the cardiac cycle. The contraction of the muscle cells destroys the stimulus, whether it was produced by a stimulus, from the heart itself or by one conducted to it from some other quarter. Thus it may be explained why that spot in the heart, at which the stimulus is most, rapidly formed again to the point of effective strength, always gives the rate of contraction