240 



PHYSIOLOGY OF THE HEART. 



[CH. xx. 



apparatus, which consists of a cylinder covered with smoked paper, revolving 

 with a definite velocity. The point of the lever writes upon the paper, and 

 a tracing of the heart's impulse or cardiogram is thus obtained. 



Tube to communicate 

 with tambour. 



Tambour. 



Ivory Tape to attach the instrument 

 knob. to the chest. 



Fig. 238. Cardiograph. (Sanderson's.) 



Fig. 240 represents a typical tracing obtained in this way. 

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

 second larger rise by the ventricular systole ; the downstroke 



Screw to regulate elevation of lever. 



Writing lever. 



Tambour. 



Tube of cardiograph. 



Fig. 239. Marey's Tambour, to which the movement of the column of air in the first 

 tambour is conducted 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. 



represents the pause, the tremors at the commencement of which 

 are partly instrumental and partly caused by the closure of the 

 semilunar valves. 



Another method of obtaining a tracing from one's own heart 

 consists in dispensing with the first tambour, and placing the 



