Therapeutics of the circulation / by Sir Lauder Brunton.

  • Lauder Brunton
Date:
1914
Catalogue details

Licence: Public Domain Mark

Credit: Therapeutics of the circulation / by Sir Lauder Brunton. Source: Wellcome Collection.

    34/568 page 6
    the importance of slowing the pulse-rate by rest, by cold, by drugs, or by other measures, when it tends to become too rapid. Perhaps it may be as well here that I should note that the heart, at certain periods, is resist¬ ant to external stimuli. When Captain Barclay was taking his sleep between his walks, he would be more and more ready to respond to a chance call the nearer the time came for him to begin again ; but while actually engaged in his walk, he would be too much intent upon his work to heed a call from anyone. In the same way, we find that during the period that the heart is contracting it will not respond to a stimulus which, if applied immediately after its action is over, wrould cause it to contract again. This period, which we have to consider later on, is called the refractory period. ao Fig. 1.—Diagram to show liow the blood under pressure in the aorta is shut off from the rest of the heart during diastole by closure of the sigmoid valves, a, Auricle ; ao, aorta ; v, ventricle. The Arteries: their Triple Function.—Now, if the heart is only acting for eleven hours out of the twenty-four, and is entirely cut off from the aorta by the closed aortic valves (Fig. i), what force is carrying on the circulation during the
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