164 THE CIRCULATION OF THE BLOOD 



Chauveau and Marey have been able to record and measure with much 

 accuracy the variations of the endocardiac pressure and the comparative 

 duration of the contractions of the auricles and ventricles. They placed 

 three small India-rubber air-bags or sounds in the interior, respectively, of 

 the right auricle, the right ventricle, and in an intercostal space in front of 



FIG. 161. Apparatus of MM. Chauveau and Marey for Estimating the Variations of Endo- 

 cardiac Pressure, and Production of the Impulse of the Heart. 



the heart of living animals the horse. These bags were connected by 

 means of long narrow tubes with three levers arranged one over the other 

 in connection with a registering apparatus, figure 161. The synchronism 

 of the impulse with the contraction of the ventricles is also well shown by 



FIG. 162. Tracings of i, Intra-auricular; 2, Intraventricular Pressures; and 3, of the Cardiac 

 Impulse of the Heart. To be read from left to right. Obtained by Chauveau and Marey. 



means of the same apparatus, and the causes of the several vibrations of 

 which it is really composed have been demonstrated. 



In the tracing, figure 162, the intervals between the vertical lines rep- 

 resent periods of a tenth of a second. The parts on which any given vertical 

 line falls represent simultaneous event?. It v/iU be seen that tt. Contraction 



