Revised views of the refractory period, in relation to drugs reputed to prolong it, and in relation to circus movement / by T. Lewis and A.N. Drury.

  • Thomas Lewis
Date:
[1926]
Catalogue details

Licence: Public Domain Mark

Credit: Revised views of the refractory period, in relation to drugs reputed to prolong it, and in relation to circus movement / by T. Lewis and A.N. Drury. Source: Wellcome Collection.

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    Lewis and Master® in investigating A-V conduction observed a number of new phenomena interpretable on similar lines to these. They found, when heart block is present, that over a certain period of the cycle termed by them the “ phase of interference ’ an impulse which fails to be conducted from auricle to ventricle, nevertheless influences the passage of the succeeding impulse, postponing or preventing the ventricular response. The “ phase of interference’? was found to commence immediately after the period which can be regarded as corresponding to the absolute refractory state of the A-V tissues and may be traced as far as the point at which conduction from auricle to ventricle occurs ; and the interference was regarded as due to the passage of the corresponding impulse through a limited portion of the conducting tract. Thus, when the impulse falls early, the response or non- response of the A-V tissues is gauged, not by response or non-response of the ventricle to that particular impulse, but by the presence or absence of its effect on subsequent conduction. The observations suggested a re- examination of the original curves which served to measure the refractory period of auricular muscle poisoned by quinidine and strophanthin and, when this was done, corresponding phenomena were found. In these experi- ments the absolute refractory period of the auricle, driven by the rhythmic shocks, was tested by means of break shocks falling with varied prematurity in the cycle ; certain of these gave response, certain did not ; the dividing line was drawn between these two series and we took it to represent the absolute refractory period; in thus measuring the period we followed custom. Nevertheless, the values obtained in a number of experiments were not those of the absolute refractory period as will be shown presently. Drury and Love?, in an article published with this, have fully examined the effect of veratrin upon the refractory period from the same point of view and find that when the “ phase of interference ”’ is allowed for, the absolute refractory period is not prolonged by this alkaloid though, as estimated by simple response or non-response, it seems conspicuously increased. They are able to give accurate measures of the actual and the apparent refractory period in this instance, and to show their considerable divergence. ‘To these Love® adds his more recent observations upon the action of quinidine and strophanthin upon the tortoise ventricle. The original curves of our old observations upon the effects of quinidine® and strophanthin® on the dog’s auricle give accurate measures of the apparent period ; in some instances, though by no means in all, they also allow us on re-examination to estimate the actual period. The method of obtaining the last value is fully described in Drury and Love’s article. To exemplify, we take a tabulated statement from our previous paper (NG., Table III of that article®) and republish it as present Table I. The dividing line in this table (marked R.P.) separates the periods of simple response and non- response, and measures the absolute refractory period as it was apparent to us before and after dosing the animal with quinidine. We have reconstructed this table and now include as responses, both the visible response in the
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