CIRCULATION OF THE BLOOD. 



bour tp the other. R is covered with a thin rubber membrane, 

 drawn not too tightly, against which rests a long light lever. If 

 the carotid pulse is taken, it is not necessary to cover the thistle 

 tube with rubber. The integu- 

 ment over the artery, against 

 which the tube is tightly pressed, 

 acts as such. 



If a record of the radial pulse 

 is to be taken, the thistle tube 

 should be covered in the same 

 way as the recording tambour, T 



and a Cork button cemented to FIG. ^.-Simple Sphygmograph and Car- 



diograpn. (Description in text.) 



the middle of the rubber mem- 

 brane. The button is applied to the integument over the artery, 

 the movements of the artery are transmitted to the button of the 

 receiving tambour and its rubber membrane, and this in turn is 

 transmitted to the membrane and lever of the recording tambour 

 which writes the record upon the smoked paper of the revolving 

 drum. 



Take a tracing of the carotid pulse, adjusting the receiving tam- 

 bour until a definite curve is obtained. Make out the general rise 

 and fall of the pulse pressure with each systole and diastole and 

 the secondary waves of the tracing. Explain. 



Repeat, taking a record from the radial artery. Compare the 

 sphygmographic record with palpation of the artery by the 

 finger. 



Take sphygmographic records with the spring sphygmographs 

 of Marey or Dudgeon or some other similar instrument. Compare 

 with the record taken by the tambour scheme. 



XXI. VOLUME PULSE. 



The pulse record as taken by the sphygmograph measures with 

 a fair degree of approximation the changes in pressure in an artery 

 brought about by ventricular systole and diastole, but measures 

 very inexactly the changes in volume. 



