JOHANSEN 



increase from 34.3 G to 35.4 C in less than 30 minutes. This 

 increased core temperature seemed to result initially from a 

 decrease in heat loss brought about by a vasoconstriction in the 

 body surface. Then 15 to 20 minutes after the onset of vasoconstric- 

 tion the oxygen uptake increased. The increase in oxygen consump- 

 tion was correlated with the start of shivering, which apparently 

 can be evoked in armadillos by the slightest stimulus. In fact, 

 shivering and an attendant increase in body temperature were 

 occasionally observed when the room temperature was as high as 

 30 G. When exposed to cold, the animal immediately arose and 

 tucked his head under his belly. His posture was ball-like and only 

 a very small portion of the soft skin on the ventral side was directly 

 exposed to the cold air (Fig. 9B). The increase in body temperature 

 upon a decrease in air temperature did not occur only with the first 

 cold stimulus. On the contrary, each time the temperature decreased 

 the animal's body temperature rose immediately (Figs. 10 and 11). 

 Even when the air temperature was decreased from G to -10 C, 

 and the animal already had a very high heat production, the body 

 temperature rose. On one occasion when the change was from C 

 to -6 C, the rectal temperature increased from 35.7 G to 36.1 G 

 in less than 10 minutes. During the stepwise decrease of ambient 

 temperature from 30 G to -10 G in a period of 5 hours, the total 

 increase in rectal temperature was 3.5 G (Fig. 10) and the body 

 temperature on the armor decreased about 10 G to 23 G. These 

 temperature changes occurred in a step- like pattern following the 

 changes in air temperature. Upon a sudden decrease in air tempera- 

 ture from 30 G to G, the rectal temperature rose 2 G in 40 

 minutes. But this increasewas not as great as was the total response 

 to step- reductions from 30° G to 20 C to 10 G to G. This very 

 conspicuous increase in rectal temperature upon cold exposure has 

 to my knowledge not been reported before. It may have escaped 

 notice because rectal temperatures were not continuously recorded. 

 Bartholomew, in his paper on Setonix (1956) makes the statement 

 that at -10 G, the animal kept an elevated body temperature for 

 quite some time during the exposure period. Meanwhile, he did not 

 persuade this point further in his discussion. In my interpretation, 

 this fact, so very explicitly demonstrated in the armadillo, shows 

 that the effector mechanisms that modify heat loss, like vasocon- 

 striction, etc., operate very promptly but entirely out of pace with 



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