ii 4 A MANUAL OF PHYSIOLOGY 



at any moment is a measure of the pulsatory change of 

 velocity in the arteries of the part. And by photographing 

 the movements of the flame on a travelling sensitive surface, 

 the velocity-pulse is directly recorded. 



FIG. 37. SIMULTANEOUS TRACINGS OF THE VELOCITY (UPPER CURVE) AND 

 PRESSURE (LOWER CURVE). (LORTET.) 



The tracings were taken from the carotid artery of a horse. The curve of velocity 

 was obtained by the dromograph. The dicrotic wave is marked on it. The slightly 

 curved ordinates drawn through the curves indicate corresponding points. 



The mean velocity, like the mean blood-pressure, is more 

 variable in the large arteries near the heart than in the 

 smaller and more distant arteries. Dogiel found in measure- 

 ments taken with the stromuhr (a good instrument for the 



FIG. 38. PHOTOGRAPHIC RECORD OF THE VELOCITY- PULSE OBTAINED B\ THE 

 GAS TACHOGRAPH (v. KRIES). 



The upper curve is the photographic representation of the movements of the flame, 

 and corresponds to the curve of velocity. 



estimation of mean speed), within a period of two minutes, 

 velocities ranging from over 200 mm. to under 100 mm. per 



