ORGAN THERMOGENESIS 



JANSKY: Yes, I think this does look like incomplete results 

 but I have good evidence that the metabolism in the golden hamster 

 will fall at lower temperatures. When 1 measured the highest run- 

 ning speed the values fell very rapidly at low temperatures; there- 

 fore I expect it will also happen in the white mouse, the common 

 vole, and the bank vole. 



HANNON: Did you ever compare the absolute amounts of run- 

 ning, say over a period of a day, for animals living in a cold environ- 

 ment and animals living in a warm environment? 



JANSKY: No, we measured activity only during the short- time 

 experiment. It was the forced activity or, better to say, running 

 at the highest level which could be obtained at a certain tempera- 

 ture. The animals were not adapted to definite conditions. 



HANNON: We have conducted a few experiments on voluntary 

 running of rats living in both warm and cold environments and have 

 observed a tendency for cold to reduce such activity. This would 

 seem to agree with a prediction made some time ago by Dr. Hart 

 that running is an inefficient method for augmenting heat produc- 

 tion in the cold. I would like to ask Dr. Hart if he has ever con- 

 firmed this prediction experimentally. 



HART: Yes, but I have not published it. I did some measure- 

 ments on rats a few years ago, and there seems to be a range of 

 decreasing temperatures over which running speed actually in- 

 creases in the cold, reaches a peak, and then falls off again. I 

 think Melvin Fregley has also done this type of work. 



HANNON: At certain low temperatures they do increase their 

 running speed? 



HART: The activity depends upon the temperature and on the 

 acclimation conditions. In cold acclimated rats it increases with 

 fall in temperature to about 5 G below which it declines as shown 

 in Figure 7. 



197 



