i88 



THE CIRCULATION OF THE BLOOD 



and quietly decreases to less than that of atmospheric pressure. It 

 remains low until the beginning of the next systole. For the right ven- 

 tricle the events and variations are relatively the same. 



FIG. 159. Simultaneous Registration of Curves of the Left Intra ventricular Pressure 

 (lower), the Aortic Pressure (middle), and the Cardiac Impact (upper). Time, o.oi of a 

 second. (Hiirthle.) 



A 



ft 



200 

 ISO 



60 



0,1 



0,6 



0,7 



as $eb 



Systole 



Diastole/. 



FIG. 1 60. Schematic Cardiogram I, and Intraventricular Pressure Curves II, from the 

 Dog. The ventricular pressure curve of the descending type is represented by the dotted 

 line. Pressure in millimeters of mercury, time in tenths of a second. (Hiirthle.) 



In order to determine the endocardiac pressure communication must 

 be established with the cavities of the heart. This is accomplished by a 

 tube known as a sound, which is introduced into the left ventricle by 

 passing it down the common carotid artery, or into the right auricle and 



