Ten subjects immersed an index finger in water at 0.75°C for 40 minutes. Two-edge threshold discrimination was tested during cooling of the finger and subsequent spontaneous rewarming due to cold vasodilatation. There was a marked deterioration of tactile discrimination at finger skin temperatures below about 8°C, although the curve showing the mean decrease of numbness with increasing skin temperature was displaced relative to the curve showing the mean increase of numbness with decreasing skin temperature. Tactile discrimination was also tested on five subjects at each of six water bath temperatures (2°, 4°, 6°, 8°, 15° and 30°C). At each temperature the finger was immersed for 20 minutes and the finger circulation arrested after the first 5 minutes. There was little impairment of two-edge discrimination after 15–20 minutes immersion of the finger at temperatures of 6°C or higher. At 4°C there was marked impairment, and at 2°C all subjects experienced complete numbness at the test site.
Submitted on May 18, 1959
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