THE HEART BEAT. 547 



recording tambour and recorded on a kymographion. A simple 

 and effective cardiograph may be made by pressing a funnel 

 against the skin over the apex and connecting the stem of the 

 funnel by tubing to a suitable recording tambour. The car- 

 diograms obtained by such methods have been the subject of 

 much discussion. The form of the curve varies somewhat with 

 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. 229, 7, and a curve more difficult to interpret in 

 Fig. 229, 8. It should be borne in mind that the cardiograph curve 

 is partly a pressure curve and partly a volume curve, that is, the 

 changes in volume as well as the changes in pressure of the heart 

 during systole will affect the instrument. 



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. 230. Synchronous record of the intra ventricular pressure (F), and the aortic 

 pressure (A) : S, The time record, each vibration = ^ sec. ; 0-5, corresponding ordi- 

 nates in the two curves; 1 marks the opening ot the semilunar 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 

 carotid or subclavian artery, or through the left auricle or ventricle. 

 The sound is then connected to a suitable recording apparatus by 

 rigid tubing filled with liquid. The changes in pressure in the 

 ventricle are extensive and very rapid. To register them accu- 

 rately the recording instrument must respond with great prompt- 

 ness and at the same time must be free from inertia movements. 



