IFVING 



the way that the central nervous system handles its appreciation 

 of this stimulus. Thus, after a series of exposures the organism 

 appears to gain confidence in itself. There is every evidence that 

 the discharge of cold receptors proceeds at the same rate, but the 

 change in the sensation of cold is localized in the sensory cortex; 

 that is, there is an habituation to cold. This can be suppressed by 

 anxiety. 1 would think that possibly the central habituation may often 

 be of much greater importance than peripheral heterothermy as 

 a mechanism of cold adaptation. 



IRVING: I would like to know if anyone has ever demonstrated 

 that the discharge of the peripheral sensory endings is maintained 

 during cold exposure. 



EAGAN: We only have indirect evidence of this. Dr. Hensel 

 has not done it, but 1 believe Glasserput on a demonstration before 

 the Physiological Society. He had a subject who was accustomed 

 to immersing one finger in ice water six times per day and who 

 no longer gave any evidence of a pressor response or of a cardiac 

 acceleration response to this measurement. However, when the 

 subject was brought up before the group at the physiological meet- 

 ing, he did show the pressor response and the tachycardia. He has 

 made other indirect observations on experiments in which they 

 have induced anxiety in the subject, causing him to show this phys- 

 iological correlate of pain sensation. Also, he had an argument 

 which involved the use of tranquilizer drugs, and from all of this 

 he thought that the simplest explanation was that the discharge of 

 the peripheral receptors is unchanged. 



IRVING: Well, I cannot discount the operation of the central 

 part of thesystem in habituation, as distinct from peripheral adapta- 

 tion. I would say that adaptation likely involves change in the phys- 

 iological behavior of peripheral organs or tissue. I think there is 

 sure to be some alteration there; for example, the changes in some 

 of the nerves of the poikilotherms result in the blocking of their 

 conduction and excitability at a lower temperature after they have 

 become used to that temperature. That is the sort of thing I am 

 confidently looking for since we observed that the peripheral nerves 

 of cold adapted sea gulls conducted at lower temperatures than 

 when warm adapted. 



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