DOMESTIC MAMMAL ADAPTATIONS 

 DISCUSSION 



EAGAN; There are three minor points I should like to make. 

 First, Figure 1 showed that the rectal temperature of the rabbit 

 decreased in response to a moderate decrease in environmental 

 temperature. I know that this has been shown by some people, for 

 instance by Carlson (1955) * but we have not seen this — not even in 

 rabbits that were exposed to -25 C. There is no change in rectal 

 temperature in mature animals exposed at-25 Cfor several hours 

 (Eagan, 1961).** 



Secondly, Burton presented a theory on why the body tempera- 

 ture is regulated at about 37 G. This theory is presented in the 

 first chapter of Man in a Gold Environment (Burton and Edholm, 

 1955)*** to support the suggestion that the level of body tempera- 

 ture adopted by the hoineotherms has something to do with the 

 stability of temperature regulation. It is a matter of choosing a 

 temperature which favors economy in physiological function over 

 the widest range of environments. 



KLEIBER: What is that theory? 



EAGAN: I would refer the listeners to the original work cited 

 above. Briefly, the regulated body temperature is that one from 

 which a deviation will cause the change in heat production (Arrhen- 

 ius' law) to be balanced by the change in heat loss (Newton's law 

 of cooling), at the 25 C annual isotherm where homeothermic ani- 

 mals are believed to have originated. 



*Carlson, L. D. 1955. Interrelationship of circulatory and metabolic factors, 

 pp 13-51 in Ferrer, M. Irene, Ed., Cold injury (Trans. Third Conf.). Josiah Macy, 

 Jr. Foundation, New York. 



**Eagan, C. J. 1961. Reactive error in the measurement of rectal temperature 

 in the cold. AAL TN 59-20, USAF Arctic Aeromed. Lab., APO 731, Seattle, Wash. 



***Burton, A. C. and O. G. Edholm. 1955. Man in a cold environment. Edward 

 Arnold (Publishers) Ltd., London. 



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