284 



THE CIRCULATION IN THE BLOOD-VESSELS [CH. XXI. 



Chauveau's instrument is shown in 



was improved by Chauveau. 

 fig. 283. 



It consists of a thin brass tube, a, in one side of which is a small perforation 

 closed by thin vulcanised indiarubber. Passing through the rubber is a fine lever, 

 one end of which, slightly flattened, 

 extends into the lumen of the tube, 

 while the other moves over the face 

 of a dial. The tube is inserted into 

 the interior of an artery, and liga- 

 tures applied to fix it, so that the 

 "velocity pulse," i.e., the change of 

 velocity with each heart-beat, may 

 be indicated by the movement of 

 the outer extremity of the lever on 

 the face of the dfel. 



In order to obtain the 

 actual value of these move- 

 ments in terms of velocity, the 

 instrument must be calibrated 

 beforehand. The next dia- 

 gram, fig. 284, shows how the 

 instrument may be adapted 

 to give a graphic record. 

 The movements of the pen- 

 dulum are brought to bear upon a tambour B, which communicates 

 by a tube with the recording tambour C. If the mass of the pen- 

 dulum is small, the accuracy of the instrument is considerable. 

 Fig. 285 shows the tracing obtained from the carotid artery of 

 the horse. The pressure curve is placed below it for purpose of 

 comparison. The tracing shows the effects during the time corre- 

 sponding to one cardiac cycle. On both curves the upstroke is the 





FIG. 283. Diagram of Chauveau's Dromograph. a, Brass 

 tube for introduction into the lumen of the artery, 

 and containing an index needle, which passes 

 through the elastic membrane in its side, and 

 moves by the impulse of the blood current ; 

 c, graduated scale, for measuring the extent of the 

 oscillations of the needle. 



FIG. 284. Chauveau's Dromograph connected with tambours to give a graphic record. 



effect of the ventricular systole ; this terminates at the apex of the 

 first small curve (between the vertical lines 3 and 4) on the down- 

 stroke of the pressure curve, the rest of the downstroke until the 

 commencement of the next systole (line 5) corresponds with the 

 ventricular diastole. Beyond the line 4 is a larger secondary wave, 

 which is known as the dicrotic wave ; the smaller post-dicrotic waves 



