On the local reactions of the arterial wall to changes of internal pressure

MY attention was first directed to these phenomena by the occurrence of curves like that reproduced in Fig. 11. In the course of experiments on vaso-dilator reflexes I sometimes observed what looked like a reflex of this kind, in a limb of which the nerves had been divided; the figure _ reproduced shows the effect of a fall of arterial pressure produced by exI citing the central end of the depressor nerve on the volume of the hind leg of the rabbit, the sciatic and the nerves accompanying the femoral artery having been cut. It will be noticed that as long as the fall of blood-pressure lasts there is a passive diminution of volume in the limb, but that as soon as the previous height of blood-pressure is attained, on cessation of the excitation, there is a considerable expansion of the limb lasting for some time. Such a curve would usually be explained by stating that Fig. 1. Effect of depressor excitation on there was present all through the volume of enervated leg. Upper curve blood-pressure, next below it volume of excitation a relaxration of the vessels, leg, upper of two chronographs-period but that it was prevented from showof excitation of depressor nerve, lower ing itself in an actual expansion of one-time in 10 sec. intervals. the limb by the simultaneous fall of blood-pressure; although it was