A MANUAL OF PHYSIOLOGY 



often not the case with human cardiograms, measure out the time- 

 value of the various events in the cardiac revolution. 



For the cardiograph, a small glass funnel, or thistle tube, the stem 

 of which is connected with the recording tambour, may be sub- 

 stituted, the broad end of the funnel being pressed over the apex-beat. 



17. Sphygmographic Tracings. Attach a Marey's sphygmograph 

 (Fig. 31, p. 93) to the arm. Fasten a smoked paper on the plate D. 

 Apply the pad C of the sphygmograph to the wrist over the point 



FIG. 86. MAREY'S TAMBOUR. 



where the pulse of the radial artery can be most distinctly felt. 

 Adjust the pressure by moving the screw G. The writing-point of 

 the lever E will rise and fall with every pulse-beat. When every- 

 thing is satisfactorily arranged, set off the clockwork which moves 

 the plate D, and a pulse tracing will be obtained. Study the 

 changes which can be produced in the pulse curve (a) by altering 

 the position of the body (sitting, standing, and lying down) ; (b) by 



exercise (Fig. 88) ; (c) by 

 inhalation of 2 drops of 

 amyl nitrite poured on a 

 handkerchief by the de- 

 monstrator (Fig. 89) ; (d) 

 by raising the arm above 

 the headland letting it 

 hang at the side ; (e) by 

 compression of the brachial 



FIG. 87. DUDGEON'S SPHYGMOGRAPH. 



artery at the bend of the elbow ; (/) by altering the pressure of the 

 pad. Varnish the tracings after marking on them the conditions 

 under which they were obtained. 



A Dudgeon's sphygmograph (Fig. 87) may also be employed. 

 Or a small glass funnel or thistle tube connected with a recording 

 tambour may be pressed over the carotid artery. The lever of the 

 tambour writes on a drum, on which at the same time half or quarter 

 seconds are marked by an electro-magnetic signal. 



