Circadian Rhythms in the Feeding Behaviour of CBA Mice

Abstract

MANY vital processes have marked diurnal rhythms in natural circumstances; and in the laboratory, even under the most constant conditions possible, they still show cycles with a period approximating 24 h (‘circadian rhythms’¹). From his observations on rats, however, Siegel² concludes that the diurnal rhythm in the feeding behaviour of this species disappears in 6–10 days in animals kept under continuous light. (The same conclusion was previously reached by Baker³, but in our opinion on the basis of an inadequate analysis of the feeding behaviour of his animals.) This conclusion was justly criticized by Aschoff⁴; Siegel's pooling of data for a group of subjects may have obscured the existence of non-synchronous cycles in the different individuals. Therefore, as a preliminary to other investigations on the physiological mechanisms of feeding behaviour in mammals, we have re-investigated this point.