mviNG 



such increase in bodytemperature. These measurements were made 

 during a normal regime with the team pulling a loaded sled and with ' 

 three to five minute rest breaks every 15 minutes. 



IRVING: These were trained? 



JOHANSEN: Yes, eventually. They were not trained at the start 

 of the season, of course, but they were gradually trained during the 

 course of the winter. 



EVONUK: What was your environmental temperature, Dr. 

 Morrison? 



MORRISON: It was in February or March; the temperature was 

 near 0° C. 



JOHANSEN: I have done similar studies on smaller, well- furred 

 arctic mammals, like the muskrat, and if 1 dispense with their 

 avenues for heat loss, for instance by occluding the tail as a heat 

 exchanger, then they show a very high body temperature. In other 

 words, heat loss through the feet and the nose and panting is not 

 enough to keep them at a normal body temperature. 



ADAMS: There were also some data on beagles* showing that 

 voluntary exercise terminates at a particular level which seems to 

 be determined by the body temperature. The rate of body heating 

 is decreased with training. Untrained dogs will have a more rapid 

 rate of increase in body temperature when exercised on a tread- 

 mill, whereas trained dogs will show a slower rate and will reach 

 a particular rectal temperature in a much longer time. 



JOHANSEN: I can tell you that just harnessing up a dog team 

 makes them quite excited; it is enough to increase their body tem- 

 perature more than one degree. 



HANNON: Dr. Durrer and I have done a lot of work related to 

 this problem of insulation and metabolism of well- furred, well- 

 insulated dogs versus those that are not so well insulated. Thus, 



* Young, D. R., et al. 19 59. J. Appl. Physiol. 14:839, 



164 



