THE HEART BEAT. 



501 



the air of the tambour which are transmitted through tubing to a 

 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 



Fig. 210. Marey's cardiograph. The button on the tambour is pressed upon the 

 chest over the apex. The movements are transmitted through the tube to the right to a 

 recording tambour. 



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- 



Fig. 211. Two cardiograms from the same individual to show characteristic records: a, 

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



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. 211, 7, and a curve more difficult to interpret in 

 Fig. 211, 8. It should be borne in mind that the cardiograph curve 



