522 CIRCULATION OF BLOOD AND LYMPH. 



different distances from the heart and the pulse wave as it passes by 

 a given point in each artery may be recorded by some convenient 

 apparatus, such as can be devised in any laboratory. If the waves 

 are recorded on a rapidly revolving kymographion whose rate of 

 movement can be determined, then the difference in time in the 

 arrival of the pulse wave at the two points is easily ascertained. 

 That there is a perceptible difference in time one can easily demon- 

 strate to himself by feeling simultaneously the pulse of the radial 

 and the carotid arteries. If this difference in time is determined 

 for two arteries for instance, the femoral and the tibialis anterior 

 and the distance between the tw r o points is recorded, we have 

 evidently the necessary data for obtaining the velocity of the 

 pulse wave in the arteries of that region. A record of this kind 

 is shown in Fig. 211. 



Fig. 211. To illustrate the method of determining the velocity of the pulse wave 

 in man. Shows record of the pulse at two points on the leg at a known distance apart. 

 The difference in time is given by the verticals dropped from the beginning of these waves 

 to the time curve. This last is made by the vibrations of a tuning fork giving 50 vibra- 

 tions per second. The difference in this case was equal to 0.07 sec. 



The results obtained by various authors indicate that the velocity 

 varies somewhere between 6 and 9 meters per second for adults. 

 The figures published by later observers show also that the velocity 

 is somewhat greater in the upper extremities (7.5 m. for carotid- 

 radial estimation) than in the descending aorta (6.5 m. for carotid- 

 femoral estimation).* The average of thirty determinations made 

 in the author's laboratory upon medical students shows that the 

 velocity in the leg (femoral-anterior tibial) is 6.1 m. when the 

 records are made upon the same leg, and 7.4 m. when the record 

 for the femoral is taken from one leg and that for the anterior tibial 



*Edgren, " Skandinavisches Archiv f. Physiol.," 1, 96, 1889. 



