HETEROTHERMY IN HOMEOTHERMS 



one student was sitting for 100 minutes in sparse clothing in a room 

 at G, a toe cooled, in 40 minutes, below 10 G and then warmed in 

 two typicalslowwarmingcycles.Thetoesofthe other student cooled 

 to 5 G at 65 minutes and were colder for the remainder of the 100 

 minute test period. Duringthetests the students studied for examin- 

 ations and neither expressed or showed much disturbance by the 



o 

 cold. At 6 G the toes of one became insensitive to light touch, but 



both individuals remained sensitive and alert to small thermal 



o 

 changes when their toes were 8 G. One of them notified me that a 



certain toe was rewarming while its change was recorded from 



o 



10.0 G to 10 .2 G and remarked upon similarly small cooling before 



the change was recorded. 1 suspect that their peripheral circulation 

 is carefully monitored through alert sensations of temperature. Ex- 

 posure to cold must train the conscious and unconscious observation 

 of temperature for precise and vigorous reaction to meet temporal 

 and topographic requirements (Fig. 4). 



In the same condition and similar scant clothing, the toes of a 

 young airman, who had been for two years an assistant in the Aero- 

 medical Laboratory at Ladd Air Force Base, Alaska, cooled to 10 

 C in eight minutes and were very uncomfortable. At 14 minutes they 

 were very painful, and his general discomfort became so great in 

 41 minutes that 1 asked him to give up for fear that his violent shi- 

 vering would be injurious (Fig. 5) . 



1 was at first unimpressed when one of the students told me that 

 he had noticed sweating in his armpits while he was exposed to cold. 

 When the adhesive tape holding thermocouples to a finger and toe 

 were removed after his cold test, he pointed to droplets of sweat on 

 rewarming fingers that had not yet reached 20 G, Airman Henson 

 also looked for and showed me droplets of sweat on his fingers and 

 toes as he was rewarming but still shivering. The paradoxical ap- 

 pearance of sweat on cold skin may give a clue to a common process 

 of regulation in the simultaneous sweating and warming of cold tis- 

 sues. 



In their two years in Alaska the two students had developed the 

 ability to work undisturbed while exposed to cold that we could not 

 stand. Although they felt no pain in fingers and toes so cold as to be 

 extremely painful for a person unpracticed in exposure, their 



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