METABOLISM STUDIES ON THE WILD RAT

Abstract

Numerous measurements of the basal metabolism of the albino rat. have been made. They are not wholly uniform. Even in the researches in which the Nutrition Laboratory has cooperated measurable differences in the basal metabolism of this animal have been noted. Thus, Horst, Mendel, and Benedict conclude that the basal metabolism of adult [female], albino rats, living at an environmental temp. of 26[degree] C. but measured at 28[degree] C, about 24 hr. after food, is from 600 to 700 calories per sq. meter of body surface per 24 hr. Benedict and MacLeod conclude that a standard value for 5 albino rats would be 720 calories and for [male] rats 800 calories. In the authors'' series of wild rats the basal metabolism at 28[degree] C. was in all cases distinctly high. The average of all the basal measurements is 942 calories and the average of those obtained only on the 1st day of measurement is 1010 calories. Here it is a question whether domestication has a rapid and pronounced influence, or whether it is a matter merely of adjustment of the wild rat to a new environment with less fright. The authors believe that the terror did not obtain, even in these 1st day''s measurements, for the extraordinarily quiet repose of these animals astonished them. The basal heat production of the wild rats per 200 gm. body weight per 24 hr. was likewise higher in the 1st measurement than in subse- quent measurements, but averaged 27 or 28 calories as compared with an average of about 20 calories found with the albino rats measured at 28[degree] C. On either basis of computation, therefore, the wild rat has a perceptibly higher metabolism than the albino rat.