224 



HUMAN PHYSIOLOGY 



means of any of the various forms of cardiograph, one of 

 the simplest consisting of a receiving and recording tam- 

 bour connected by means of a tube (Fig. 112). (Practical 

 Physiology, Chap. XL) 



FlO. 112. Cardiograph consisting of a Receiving Tambour, with a button on the 

 Membrane which is placed upon the Cardiac Impulse, and a Recording 

 Tambour connected with a Lever. 



The form of the trace varies according to the part of the 

 heart upon which the button is placed, but it has the char- 

 acter shown in Fig. 113 

 if the button is upon 

 the cardiac impulse. 



At the moment of 

 ventricular systole the 

 lever is suddenly 

 thrown up to a certain 

 level (a to b). From 

 this point it suddenly falls slightly (6 to c), but is maintained 

 during the ventricular systole above the abscissa (c to d). 

 At the end of the ventricular systole, as the heart falls 

 away from the chest wall, the lever falls to its original level 

 (d to e). In many tracings a small rise of the lever may 



FIG. 113. Cardiographic Trace, a to d, 

 Ventricular Contraction. 



