A STUDY OF THE ADJUSTMENT OF PERIPHERAL VASCULAR TONE TO THE REQUIREMENTS OF THE REGULATION OF BODY TEMPERATURE

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Abstract
Using the vol.-pulsation of the finger as an index (Burton, 1939), the rhythmic fluctuations of peripheral vascular tone was studied at different environmental temps. Vasoconstrictions due to external or "psychic" stimuli may be distinguished from "spontaneous" vasoconstrictions, since the latter are not accompanied by simultaneous changes of skin resistance (psychogalvanic response). At "comfortable" temps., between 24 and 28[degree]C, the avg. interval between vasoconstrictions is 50-60 secs. This increases with raised and decreases with lowered en-vironmental temp. With the subject immersed in a well-stirred water bath, at constant temp., the vasomotor rhythm is essentially unaltered. The intermittence of vascular tone is apparently not due to a corresponding intermittence of skin temp., which has too great a thermal lag to provide a rhythmic mechanism. The efficiency of the modification of the fluctuation of tone to the thermal requirements is demonstrated by the constancy of the avg. value taken over 5 min. intervals, at different levels in baths of different temps. The amplitude of fluctuation of flow is similar in different normal subjects, amounting to about [plus or minus] 30% in a series of flow detns. The reflex adjustment of peripheral blood flow in temp. regulation consists in the modification of a vascular tone which is intrinsically fluctuating in character.