206 



THE CIRCULATION OF THE BLOOD AND LYMPH 



p. 193). Apply the button of a cardiograph (Fig. 27, p. 90) 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 (Fig. 99). Set the drum off at a fast speed, 

 take a tracing, and varnish it. Compare with Fig. 28 (p. 91), and if 

 the tracing is sufficiently typical, as is often not the case with human 

 cardiograms, measure out the time-value of the various events in the 

 cardiac revolution. 



Fig. 99. Marey's Tambour. 



For the cardiograph, a small glass funnel, or thistle-tube, 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 8. Sphygmographic Tracings. Attach a Marey's sphygmograph 

 (Fig. 37, p. 165) 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 satisfactorily arranged, set 

 off the clockwork which 



Fig. 100. Dudgeon's Sphygmograph. 



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) ; (6) by exercise 

 (Fig. 10 1) ; (c] by inhalation of 2 drops of amyl nitrite poured on a hand- 

 kerchief by the demonstrator (Fig. 102); (d) by raising the arm above 

 the head and letting it hang at the side ; (e) by compression of the brachial 

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

 V arnish the tracings after marking on them the conditions under which 

 they were obtained. 



A Dudgeon's sphygmograph (Fig. 100) may also be employed. In 

 this the clockwork carries the strip of blackened paper along beneath 



