ELEMENTARY EXPERIMENTAL PHYSIOLOGY 57 



2. The Arterial Pulse. 



(a) With the finger, compress and relax the arterial tube near the 

 tap at regular rhythmic intervals of about a second, so as to imitate 

 the interrupted inflow of blood from the heart or compress the syringe 

 rhythmically at this rate. Note the effect of this upon the arterial 

 and venous pressures, and study the further effect of constricting 

 the arterial tubes near the capillaries upon the movements of each 

 of the columns of fluid. 



(6) Place a finger on the arterial tube and note the expansion, 

 the pulse, with each rhythmic inflow, and repeat the observation on 

 the venous tubes . Explain any difference which may be observed . 



II. The Pulse in Man. 



1. Relation to the Cardiac Impulse. 



(1) Place a finger of the left hand on the radial artery at the 

 right wrist while feeling the cardiac impulse with the right hand, 

 and note what is felt in the artery. Determine whether the change 

 is simultaneous with the cardiac impulse. 



(2) Does the wave develop simultaneously throughout the arterial 

 system or does it pass out to the periphery ? Place one finger over 

 the carotid and another over the radial artery and time the appear- 

 ance of the wave under each. 



(3) Place the finger on the radial artery of a companion and study 

 the pulse as to (a) rate, (6) rhythm, (c) tension, (d) volume, (e) form of 

 wave. 



(1) Rate. Count the pulse for half a minute. This gives the rate 

 of the heart beat. (2) Rhythm. Note whether the pulse is regular 

 or irregular as to the rate and as to the strength of the individual 

 beats. This indicates regularity or irregularity in rate and strength 

 of the ventricular contractions. (3) Volume. A. big pulse means a 

 marked difference between the maximum and minimum pressures 

 in the artery. (4) Tension or force of the pulse wave (maximum 

 systolic pressure). This may be estimated by placing the middle 

 finger on the radial pulse, laying the forefinger on the artery just 

 above it and pressing on the vessel till the pulse is no longer felt 

 under the middle finger. If a recurrent pulse comes through the 

 palmar arch this may be obliterated by pressure with the ring 

 finger distally to the middle finger. (5) Form of the Pulse Wave. 

 Does the wave come up suddenly and disappear suddenly or 

 gradually ? Can more than one crest be felt on the wave ? If 

 a second crest can be felt it is the dicrotic crest and the pulse is 

 said to be dicrotic. 



(4) The Sphygmograph. Using Dudgeon's or Marey's sphygmo- 

 graph, under the direction of the demonstrator, take a tracing of 

 the radial pulse, (i) See that the clockwork of the instrument is 

 wound up. (ii) Feel the radial pulse (note its rate), (iii) Mark 

 the artery with an aniline pencil, (iv) Rest the back of the wrist 

 upon a book or other support with the hand slightly dorsi-flexed. 



