Of the influence of certain drugs on the period of diminished excitability / by Sydney Ringer and Harrington Sainsbury.

  • Sydney Ringer
Date:
[1883]
Catalogue details

Licence: Public Domain Mark

Credit: Of the influence of certain drugs on the period of diminished excitability / by Sydney Ringer and Harrington Sainsbury. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    6/20 page 352
    Hence the moment of break recorded on the cylinder alone corresponded to the moment of stimulation. Such an apparatus then records accurately the moment of stimula- tion, at the same time it allows us, by means of the metronome, to regulate at will the interval between two successive stimuli. To avoid criticism it may be here stated that the exact measurement of changes in duration was not attempted, the question which it was sought to answer was whether shortening or lengthening of certain periods did occur; this the apparatus here described enabled one definitively to determine. Since lengthening or shortening, rather than by exactly how much the one or other obtained, was that which concerned us, it was sufficient to note the position of the indicator on the stem instead of taking the actual number of beats as marked on the metronome scale for each position of the indicator, or indeed instead of timing the rate accurately by the watch for each such position. Hence metronome 1, i.e. with the indicator at the topmost mark, indicated the slowest rate, metronome 32 the quickest rate. This range in the positions of the indicator from 1 to 32 gave a considerable range in rate, amounting approximately to a multiplication of the rate by two, or a little in excess of this. For the rest the apparatus used consisted of a Roy’s tonometer and revolving drum. The heart was fed with a mixture of dried bullock’s blood dissolved in water and further diluted with two and a half times its volume of saline solution 075 per cent. Of this mixture 100 c.c. were used in each experiment. The common English frog (R, temporciria) was throughout emploj-ed. It was important in these experiments that the heart should not beat spontaneously or at any rate that the spontaneous beats should be infrequent, the ligature was hence tied low so as to include part of the ventricle, the upper third where possible. The experiments were made during the months of June, August and September, 1882. The mode of experimentation was as follows:—the metronome being set at some given rate, the cylinder was started and two successive stimuli thrown into the heart. The result might be a single contraction or two contractions; if two contractions, these might be quite separate, the diastole of the first contraction being completed before the second systole commenced, or there might be fusion more or less complete. If but one contraction resulted the metronome was set at a slower rate, if two discrete or but partially fused contractions it was set at a quicker
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