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A MANUAL OF PHYSIOLOGY 



tube into its distal end. Fill the tube with water, and notice that 

 the valves support it. Cut open the aorta just between two adjacent 

 segments of the valve, and notice the pockets behind the segments, 

 and how they are related to each other, and connected to the wall of 

 the vessel. 



14. Sounds of the Heart. (a) In a fellow-student notice the 

 position of the cardiac impulse, the chest being well exposed. Use 

 both a binaural and a single-tube stethoscope. Place the chest-piece 

 of the stethoscope over the impulse, and make out the two sounds 

 and the pause, (b) With the hand over the radial or brachial artery, 

 try to determine whether the beat of the pulse is felt in the period 

 of the sounds or of the pause, (c) Listen with the stethoscope over 

 the junction of the second right costal cartilage with the sternum, 

 and compare the relative intensity of the two sounds as heard here 

 with their relative intensity as heard over the cardiac impulse. 



15. Cardiogram. Smoke 

 a drum, and arrange a 

 recording tambour and a 

 time -marker beating half 

 or quarter seconds to write 

 on it (Fig. 60, p. 170). 

 Apply the button of a 



FIG. 68A. DUDGEON'S SPHYGMOGRAPH. 



cardiograph (Fig. 18, p. 79) over your own cardiac impulse, and 

 fasten it round the body by the bands attached to the instrument. 

 Connect the cardiograph by an indiarubber tube with a recording 

 tambour. Set the drum off at a fast speed, take a tracing, and varnish 

 it. Compare with Fig. 19 (p. 80), and measure out on the cardio- 

 gram the time-value of the various events in the cardiac revolution. 



For the cardiograph, a small glass funnel, the stem of which is 

 connected with the recording tambour, may be substituted, the broad 

 end of the funnel being pressed over the apex-beat. 



1 6. Sphygmographic Tracings. Attach a Marey's sphygmograph 

 (Fig. 26, p. 90) to the arm. Fasten a smoked paper on the plate D. 

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

 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 everything is satis- 



