Influence of Resilience of Arterial Wall on Blood-Pressure. 181 



recorded by means of cannula: placed in the arteries and connected with 

 Hiirthle manometers. Hiirthle* and others have recorded previously higher 

 readings of pressure in the femoral than in the carotid artery of the dog. 

 Tigerstedt ascribed these to reflection of the primary pulse wave without 

 change of sign and addition of the reflected to the primary wave in the 

 femoral artery.f The difference of the systolic pressures in the arm and 

 leg in aortic cases was ascribed by L. H. and his co-workers to the better 

 conduction of the systolic wave crest in the leg arteries, which were assumed 

 to be in a more contracted and harder state. 



This view was confirmed by experiment, for it was found, on placing the 

 legs and buttocks of the patients in a hot bath, the difference between the 

 readings of arm and leg arteries was abolished, and this was ascribed to 

 the expanding and softening of the contracted walls of the latter. Also, in 

 the case of healthy young men placed in the horizontal posture, while it was 

 found that the leg and arm readings of systolic pressure were normally the 

 same, these were rendered temporarily unequal after the subjects had run 

 twice up and down a long flight of stairs (particularly if the arm were placed 

 in hot water beforehand) ; the heart was thereby made to beat forcibly, while 

 the leg arteries became more contracted, so the crest of the wave was better 

 conducted in them than in the arm arteries. By placing one arm in hot 

 water, it was found possible to render the reading different in the two 

 arms, even in the resting subject, much more so after a short period of 

 violent exercise. If the wrist alone were placed in hot water, the radial 

 gave a lower reading than the brachial, but if the elbow were placed in 

 hot water, readings of brachial and radial were equal, both being lower 

 than in the other and cooler arm ; bandaging the hand tightly made no 

 difference to the reading. 



The conclusion arrived at was that the inequality was due to an altered 

 condition of the arterial wall and not to diminished peripheral resistance, 

 and these experiments led to the conception that the nature of the arterial 

 wall affects the conduction of the systolic wave, and that the blood-pressure, 

 as ordinarily measured by a sphygmometer, by the method of obliteration 

 of the pulse, depends not only on the pressure wave produced by the heart, 

 but also on the effect on this wave of the arterial wall, a new factor which has 

 not hitherto been taken into account. 



A difference of pressure between the arm and leg readings has been noted 

 by several observers in cases where the arteries are thickened and hardened 

 as in old people. This difference has been ascribed to an error in the 



* ' Arch. f. d. ges. PhysioL, : vol. 47, p. 32. 



+ ' Lehrb. d. physiol. dee Kreislaufes,' 1893, p. 352. 



