THE EVENTS OF THE HUMAN CARDIAC CYCLE 109 



with the polygraph, in which a delicate lever replaced the usual 

 pen, which is heavy for the purpose ; and an electrocardiogram 

 taken in Professor Waller's laboratory with an Einthoven " string 

 galvanometer." The jugular curve has been marked with the 

 letters used by Mackenzie and employed in the text. The 

 electrocardiogram has been marked with the letters used by 

 Einthoven ; P represents auricular contraction, R and T are the 

 result of ventricular contraction. The curves were obtained from 

 a lad with a prominent jugular pulse. 



The a-c interval, as measured in the jugular tracing, in the 

 first and last curves is -14 and '12 sec. respectively. The time 

 interval between auricular and ventricular contraction, as measured 

 in the electrocardiogram, is '11, '12, and '12 respectively. It will 

 be seen that the delay in the appearance of " a " and " c " waves 

 in the neck is practically identical, namely '12 sec., and that the 

 a-c interval is, as taken by this method, less than \ sec. The 

 delay of '12 sec. in the appearance of the waves in the neck is the 

 uncorrected value. A deduction of '04 sec. must be made for 

 instrumental delay in the jugular curve. The true value is 

 consequently -08 sec. 



The figures given are in agreement with others obtained from 

 the same subject, and accord very closely with the estimated 

 values quoted in the text. 



BIBLIOGRAPHY 



1 Bard, (a) Jour. d. physiol. e. d. pathol. gen., inai 1906, pp. 454-459. 

 (6) Ibid., pp. 466-479. (rj Archiv. d. .Maladies du Coeur, &c., juin 1908, 

 No. 6. 



1 Uaum, Verhandl. d. phys.-nied. Gesell. z. Wiirzburg, N. F., Bd. 38, 

 1906,8. 61-102. 



' Hayliss and Starling, Internal. Monatssch. f. Anat. U. Pliys., Bd. 11, 

 Hft. 9, 1894, pp. 426-435. 



4 Belslci, Zeitsch. f. kliu. Med., Bd. 57, Hft. 5 u. 6, 1905, B. 565. 



Briicke, Vorle*ungen iiber Physiologic, Wien, 1885, Bd. 1, Aufl. 4, s. 

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Chuuveau and Faivre, Gaz. mcd. de Paris, T. xi., 1856, p. 406. 



7 Ciuiuveau and Marey, ibid., 1861, p. 675. 



8 Kdyren, Skand. Archiv. f. Physiol., Bd. 1, 1889, s. 67-151. 



Einthoven and Gelitk, Archiv. f. d. ges. Pliysiol., Bd. 57, 1894, s. 

 617-639. 



10 Erlanyer, Johns Hopkins Bulletin, No. 177, vol. 16, 1905, pp. 394-397. 



