THE PULSE 



213 



For recording the pulse, an instrument such as that shown in Fig. 113 

 may be used. The disadvantages are that the tracings are but 

 of short length and that in the ordinary form, which is strapped 

 round the wrist, the pulse tracing is modified by the effect of pressure 

 upon the venae comites of the army. For this reason it is better to 

 employ the suspension method illustrated in the figure, in which the 

 pressure of the lever is exerted directly over the radial artery. 



Of greater service is the instrument known as the polygraph 

 (Fig. 114). With this instrument it is possible to take two tracings 

 at the same tune, and that of a time-marker. The usual combina- 

 tion is a tracing of the radial and venous pulses. 



FIG. 115. DIAGRAM SHOWING THE AVERAGE POSITION OF THE JUGULAR BULB. 



(Keith.) 



a, The jugular point, 25 min. from the sternal end of the clavicle (c); b, jugular bulb, 

 behind sternal head of sterno-mastoid and in front of first stage of subclavian 

 artery ; d, subclavian vein ; e, sternal head of sterno-mastoid ;/, superior vena cava ; 

 g, manubrium sterni. 



Such simultaneous graphic curves are valuable, since they record 

 information of the time relations and the nature of the contraction of 

 the separate heart chambers. 



The Venous Pulse in man is best recorded by applying a small 

 metal receiver (3-4 centimetres diameter, 1 centimetre deep) between 

 the two heads of origin of the relaxed sterno-mastoid muscle (Fig. 115), 

 and transmitting the pulsations by air to a delicate recording tambour. 

 By this means a tracing of the jugular bulb is obtained, where it 

 lies a little above, and about 25 millimetres external to, the inner 

 end of the clavicle. The bulb is so called because in the internal 

 jugular vein at this point is a pair of valves, and here a bulging of 

 the vessel takes place in cases of impeded flow to, or of regurgitation 

 from, the auricles. 



The venous pulse shows three main elevations (a, c, v). The exact 

 interpretation of some of these factors is still a matter of doubt. 



