Recoil Curves as shown by the Hot- Wire Microphone. 297 



The results so far obtained are consistent with accepted physiological 

 data as to the variations in the systolic output of the heart, as affected by 

 exercise, respiration or the action of vaso-constrictors and vaso-dilators. 



In conclusion, the authors wish to express their appreciation of the help 

 and assistance given to them in carrying out this work by Sir Frederick Sykes, 

 the Controller- General of Civil Aviation, and Lieut.-Colonel Cusins, Chief 

 Experimental Officer of the Signals Experimental Establishment, where the 

 work was carried out. They further desire to express their indebtedness to 

 Prof. Yandell Henderson, Dr. A. W. Stott for his kind collaboration during 

 the preliminary stages, and to Dr. P. Hamill, when correlation with the 

 electro-cardiograph was required, as well as for advice on the physiological 

 aspects of the paper. 



The authors particularly wish to recognise the help given by Mr. A. Reading, 

 who, besides providing them with a very useful subject for heart recording, 

 also manipulated the apparatus most skilfully. 



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(1) Bainbridge, F. A., ' The Physiology of Muscular Exercise,' London, 1919 ; " The 



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(2) Bainbridge, F. A., and Hilton, R., " The Relations between Respiration and the 



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(3) Barcroft, J., " Measurement of the Blood Flow through the Chest of the Goat," 



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(7) Henderson, Yandell, " The Mass Movements of the Circulation, as shown by a 



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(8) Hill, A. V., "Electrical Recording of the Pulse," 'Lancet,' 9/10/20 ; "Hot- Wire 



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(9) Krogh, August, and Lindhard, J., " Measurements of the Blood Flow through the 



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(10) Lewis, T., ' The Mechanism and Registration of the Heart Beat,' London, 1920. 



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Pulse, Arterial, Venous, and Hepatic, and of the Movements of the Heart,' 

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