ENDOCARDIAC PRESSURE 1 89 



ventricle through the jugular vein. When a cardiac sound is introduced 

 and connected with some form of pressure-recording apparatus, accurate 

 tracings of the variations in pressure during the heart-beat are obtained. 

 Chauveau and Marey recorded and measured with accuracy the 

 variations of the endocardiac pressure and the comparative duration 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 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 the heart 

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



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. 



long narrow tubes with three levers arranged one over the other in con- 

 nection with a registering apparatus, figure 161. The synchronism of the 

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

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

 which it is really composed have been demonstrated. 



