544 CIRCULATION OF BLOOD AND LYMPH. 



the instrument used, the way in which it is applied, the position of 

 the heart apex with reference to the chest wall, and with the con- 

 ditions of the circulation, and it is often difficult to give it a correct 

 interpretation. An uncomplicated form of the cardiogram is 

 represented in Fig. 230, 7, and a curve more difficult to interpret in 

 Fig. 230, 8. Owing to the number of factors that alter the char- 

 acter of these curves they have not proved to be very useful in the 

 accurate study of the character and time relations of the heart beat. 



Fig. 230. — Two cardiograms from the same individual to show characteristic records: a, 

 Beginning of systole; b-c, systolic plateau. — (After Marey.) 



The Intraventricular Pressure During Systole. — ^The best 

 analyses of the details of the systole of the ventricle have been made 

 by a study of the changes in pressure within the ventricle. For 

 this purpose a tube filled with liquid is introduced into the cavity of 

 the ventricle. A tube used for such a purpose is designated as a 

 heart-sound. For the right ventricle it is introduced through an 

 opening in the jugular vein and pushed down until it lies in the 



Fig. 231. — Synchronous record of the intraventricular pressure (V). and the aortic 

 pre.'ssure {A) '. S, The time record, — each vibration = xio sec. ; 0-5, corresponding ordi- 

 nales m the two curves; 1 marks the openmg oi the seimlunar valves; 3 (or shortly after) 

 marks the closure of these valves and the beginning of diastole. — (Hiirthle.) 



ventricle, or in some cases it may be thrust through the wall of 

 the ventricle. For the left ventricle it is introduced by way of the 



