STUDIES ON PAIN. OBSERVATIONS ON PAIN DUE TO LOCAL COOLING AND ON FACTORS INVOLVED IN THE “COLD PRESSOR” EFFECT

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Abstract
A deep, aching, painful sensation induced by immersing a part of the body in cold water was found to follow a definite pattern, namely, that regardless of strength of stimulus, pain reached its maximum in approx. 60 secs. The pain gradually subsided, giving way to a sensation of "pins and needles" which soon terminated. The mechanism whereby the pain was produced and the reason for its "adaptation" were investigated. The intensity of the pain and the total amt. of pain depended directly upon the degree of cooling[long dash]that is, the thermal gradient between the immersed part and the water. When this difference was small "adaptation" occurred. Warming the part or lowering the bath temp. abolished "adaptation." Further the pain was separate from the sensation of cold, mediated by small unmyelinated fibers of class C. A strong vasoconstriction in the part was an accompaniment of the pain and it was possible to influence the pain by vasoconstrictor drugs. This and other evidence indicated that the "cold pain" might arise in the walls of the blood vessels in response to a strong vasospasm. The elevation of blood pressure which resulted from immersing a part in cold water varied directly with the degree of cold and with the intensity of pain. Further data, however, showed that the blood pressure effect did not depend directly on either cold or pain but probably represented the patient''s reaction to pain.