SUCCESSION OF MOVEMENTS OF THE HEART. 193 



of the auricles precedes the ventricular systole, and that the 

 latter is synchronous with the impulse. 



Yarious estimates have been made of the relative time 

 occupied by the auricular and ventricular contractions. This 

 interesting point has been carefully studied by MM. Chau- 

 veau and Faivre, by auscultating the heart exposed in a living 

 animal, and establishing, by the touch, the relations between 

 the contractions of its different parts and the heart sounds. 

 These observers made a great number of experiments upon 

 horses and dogs, in which the pulse was not more accelerated 

 than the pulse of the human subject. As the result of these 

 observations, the following numbers are given as representing 

 the rhythm of the movements of the heart in man : Auricular 

 systole, 6 ; Yentricular systole, 10 ; Diastole, 8. 1 Though this 

 estimate is perhaps better than any we had before, it is evi- 

 dent from the way in which it was arrived at that it can be 

 nothing more than an approximation ; for it is impossible to 

 estimate accurately, by the stethoscope and the touch, opera- 

 tions which follow each other with such rapidity. 



This question has been at last definitely settled by the 

 late observations of Marey, who has constructed some very 

 ingenious instruments for registering the form and frequency 

 of the pulse. He devised a series of most interesting experi- 

 ments, in which he was enabled to register simultaneously 

 the pulsations of the different divisions of the heart, and has 

 succeeded in establishing a definite relation between the con- 

 tractions of the auricles and ventricles. The method of M. 

 Marey enables us to determine, to a small fraction of a sec- 

 ond, the duration of the contraction of each of the divisions 

 of the heart. 



The method of transmitting the movement from the heart 

 to a registering apparatus is very simple. It consists of two 

 little elastic bags connected together by an elastic tube, the 

 whole closed and filled with air. A pressure, like the pres- 



1 CHAUVEAU et FAIVRE, op. cit., p. 18. These authors represent the rhythm 

 by musical notes, which have been reduced to the numbers given above. 

 13 



