The rhythms of life and other essays in science / by D. Fraser-Harris.

  • David Fraser Fraser-Harris
Date:
1929
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Licence: In copyright

Credit: The rhythms of life and other essays in science / by D. Fraser-Harris. Source: Wellcome Collection.

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    slower heart-beats than the mouse or the sparrow. The heart-beat in these small animals is so fast that the pulse cannot be counted in the usual way. Until recently we had no reliable information about it, but by an electrical method it has been ascertained with great accuracy. For instance, the rabbit's heart beats at four a second. The pulse-rate, which in health is the same thing as the heart-rate, is very much slower in the cold-blooded than in the warm-blooded animals. Thus, in a fish or frog the heart contracts only about forty times in the minute, or about half the human rate. This relatively slow rate can be quickened by making the heart beat in warm salt water. A study of the warm-blooded heart proves to be full of interest. The heart can be accelerated by warmth and slowed by cold, but it is its affectability by nerve impulses that is so remarkable. It is a matter of common knowledge that the heart can be made to beat much faster at one time and slower at another through nerve impulses alone. Everybody knows that emotions can influence the heart very markedly. Thus, of course, it has come about that “ the heart ” and certain emotions are taken as
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