JOHANSEN 



large activity range of body temperature may express a specializa- 

 tion rather than a primitive condition. A truly fixed body tempera- 

 ture, fluctuating within very narrow limits, would for many species 

 be highly uneconomical, or not at all obtainable in the special envi- 

 ronments they face. This viewpoint gets support from my work on 

 the birch mouse, a rodent which shows diurnal fluctuations in body 

 temperature up to 20 C in the summer time (Johansen and Krog, 

 1959). The large activity range of the husky gives additional support. 

 The work done on the camel by Schmidt- Nielsen et al. (1957) and 

 on the rhinoceros by Albrook et al. (1958), and practically all the 

 smaller animals subjected to thoroughstudy recently show the same 

 thing (Morrison and Ryser, 1959). Let us not forget Joseph 

 Barcroft's words (1934) that every adaptation is an integration. Let 

 us remember there is more to it than just keeping a constant core 

 temperature. The effector systems involved in temperature regula- 

 tion ^have other tasks to perform, which is so strikingly apparent 

 from Schmidt- Nielsen's study on the came LI am confident that when 

 our knowledge of body temperature ranges during activity and other 

 bodily performances, as well as sleep, is extended, this will dis- 

 close a larger range of body temperatures than we are familiar with. 

 Let us not a priori let such a large temperature range be classified 

 as a primitive sign. Moreover, I feel from my work on the arma- 

 dillo that the specializations 1 have mentioned above can also develop 

 in forms of lower phylogenetic ranking and thus complicate, and 

 maybe somewhat invalidate, the body temperature range as a clear 

 measure of the phylogenetic standing. I would like to submit this idea 

 as a challenge to present concepts of temperature regulation. 



Ed. note: The discussion of Dr. Johansen's paper was postponed until the 

 following session due to lack of time. It is incorporated with the discussion of 

 Dr. Irving's paper. 



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