CH. XX.] 



CARDIOGRAPHS 



239 



Fig. 247 represents a typical tracing obtained in this way. The 



Tube to communicate 

 with tambour. 



Tambour. Ivory Tape to attach the instru- 



knob. ment to the chest. 



FIG. 245. Cardiograph. (Sanderson's.) 



first small rise of the lever is caused by the auricular, the second 



Screw to regulate elevation of lever. 



Writing lever. 



Tambour. 



Tube of cardiograph. 



FIG. 246. Marey's Tambour, to which the movement of the column of air in the first tambour is con- 

 ducted by a'tube, and from which it is communicated by the lever to a revolving cylinder, so that 

 the tracing of the movement of the impulse beat is obtained. 



larger rise by the ventricular systole ; the downstroke represents the 



FIG. 247. Cardiogram from human heart. The variations in the individual beats are due to the 

 influence of the respiratory movements on the heart. To be read from left to right. 



