The Development of Temperature Regulation in the Mouse

Abstract

The rate of cooling of living mice aged 2-24 days is always slower than that of dead mice of the same age and weight; and the rate of warming of live mice is always faster than that of dead mice of the same age and weight. At any constant external temp. over the range 15[degree]-35[degree] C. the rectal temp. of living mice is always somewhat above the outer temp. The equilibrium difference between internal and external temp. is not constant, but fluctuates rhythmically about a mean. When the difference between external and internal temp. for mice of the ages used, is plotted as a function of temp. over the range 15[degree]-35[degree] C, it is found that this difference increases to a maximum at 25[degree] C. [plus or minus] and then falls at high temps. The ascending limb of the curve has been designated the "metabolic" phase, the descending limb the "regulatory" phase. No exact description of the relation of the development of temp.-regulating ability to age can be given without the resolution of the role of these 2 phases at all ages.