THE ABSENCE OF VASOCONSTRICTOR REFLEXES IN THE FOREHEAD CIRCULATION. EFFECTS OF COLD

Abstract

The absence of vasoconstrictor reflexes in the forehead was demonstrated by the following evidence: The spontaneous rhythmic constrictions of vasomotor origin in the finger of the resting subject are absent from the forehead. The vasoconstrictor reflexes elicited by startle, awakening, a deep breath, immersion of the hand in ice water or local cold to the forehead are wholly absent in the latter. The vascular reactions of the forehead skin to local cold are like those of a sympathec-tomized digit. Constriction is gradual as the temp. of the skin falls and seems to be due to the direct effects of cold on the vessels. The reactive dilatation to cold which occurs in the fingers was not observed in the forehead skin. Occasionally, there was indication of a vasodilator reflex in the forehead skin at the time of a powerful constriction in the finger.