1913.] Lability of Arterial Wall on Blood Pressure. 367 



the pulse to the manometer. We rhythmically pulsed the tube as hard as 

 possible between thumb and finger, so that the pressure curves produced 

 were made of approximately equal amplitude. 



Fig. 1 shows the curve obtained — A, when 5 inches of rubber pressure 

 tube conducts the pressure-wave to the manometer ; B, when the conduction 

 is by 5 inches of femoral artery (human), all the branches of which have been 

 tied so that there is no leak. The " lability " of this length of artery has a 

 very great effect, as is seen by the diminution of the systolic wave and the 

 absence of " overswing " secondary waves. Fig. 2 shows — A, the curve obtained 

 from the carotid artery of a cat, conducted to the manometer by a 23 -cm. length 

 of pressure tubing ; B, when the manometer is connected by a 23-cm. length of 

 cat's artery, made up of the aorta together with the part of one carotid and one 

 femoral artery. The arrangement was such that the pulse curve could be 

 transmitted alternately by the rubber pressure tube or by the artery. Fig. 3 

 shows the effect of transmitting the pressure curve from the carotid of a cat 

 through — A, 8 cm. of rubber pressure tubing ; B, through 8 cm. of excised 

 cat's carotid. Fig. 4 shows the effect of transmitting the curves — A, through 

 6 cm. of rubber pressure tubing ; B, through 6 cm. of cat's carotid. Fig. 5 

 shows that, after hardening the 6-cm. length of carotid artery in alcohol, the 

 same result is obtained as with rubber pressure tubing. Fig. 6 demonstrates 

 the effect of 4 - 5 cm. of cat's carotid (B) on the conduction of the pressure 

 curve. Even this short length notably alters the curve, particularly in 

 diminishing the dicrotic wave. 



Fig. 7 shows the effect of connecting one end of an 8-cm. length of carotid 

 artery, closed at the other end, to the rubber pressure tube through which 

 the pressure curve was being conducted. This brings down the amplitude 

 and approximates the systolic and diastolic pressures just as effectually as if 

 the conduction were wholly through the same length of carotid. Fig. 8 — A 

 shows the curve taken from the right and left carotid of a cat. On the right 

 side the cannula was inserted as near the aorta as possible, while on the left 

 side the cannula was inserted as far from the aorta as possible. The dicrotic 

 wave is much less marked in the tracing taken from the longer length of 

 carotid. B shows tracings taken from the right and left carotid, both being 

 as short as possible. There is no noteworthy difference. We give this 

 tracing as a control, to show that the conduction by the length of artery is 

 the factor which makes the difference in A. Fig. 9 shows the pressure curve 

 of the cat taken — A, from the long length of left carotid still embedded 

 in the tissues ; B, from the short length of right carotid. In A, the dicrotic 

 wave is less evident, and the curve has a flatter top, but the difference is 

 less than in fig. 8. 



