THE REACTIONS OF THE DIGITAL ARTERY AND MINUTE PAD ARTERIES TO LOCAL COLD

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Abstract
The selective effects of local cold on the terminal pad vessels and the digital artery of the chilled finger were demonstrated by means of photoelectric plethysmographs. The digital artery does not participate in the vasoconstrictor reflexes elicited by the cold. Its later constriction during the continued application of cold appears to be due to the direct effects of the fall in temp. on the artery. The reactive dilatation which appears during the application of cold is limited to the minute pad vessels and does not involve the digital artery until the resultant rise in finger temp. permits relaxation of this artery. The effects of these reactions on the propagation of the pulse in the finger''s arterial system were studied by recording the pad pulses with high frequency galvanometers. In the usual expt. the time relations and form of the pad pulses in the chilled finger were altered only moderately and in the direction which could be predicted from the relative participation of the pad and digital arteries in the reactions to cold. In a few normal subjects, the reactive dilatation produced a pad pulse similar to that seen in chronic hypertension, thus suggesting that one of the factors responsible for the change in pad pulse form in hypertension may be the shunting of blood through direct arteriovenous communications.