546 



CIRCULATION OF BLOOD AND LYMPH. 



experiments have been made by running needles through the chest 

 wall into the base and the apex of the heart. Such needles act as 

 levers with a fulcrum in the skin, and from the movement of the 

 projecting portion it has been shown that, while the basal portion 

 of the heart moves downward during systole, the apex remains 

 more or less stationary except for the lateral movements due to 

 the rotation. 



Fig. 228. Marey's cardiograph. The button on the tambour is pressed upon the 

 chest 9ver the apex. The movements are transmitted through the tube to the right to a 

 recording tambour. 



The Cardiogram. The apex beat may be recorded easily by 

 means of appropriate tambours. Several instruments have been 

 especially devised for this purpose and are designated as cardio- 

 graphs. The cardiograph described by Marey is shown in Fig. 228. 

 It consists essentially of a tambour inclosed in a metal box. The 



Fig. 229. Two cardiograms from the same individual to show characteristic records: a, 

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



rubber membrane of the tambour carries a button which can be 

 brought to bear, under a suitable pressure, upon the apex of the 

 heart. The movements of this button cause pressure changes in 

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



