To the Editor:—
I would like to add some comment to your editorial of Oct 18 (194:231, 1965), "Circadian Rhythms."During the last several years, knowledge of circadian rhythms in animals and in man has been marked by considerable progress which clearly indicates the fundamental importance of these rhythms for medicine and biology.Your editorialist declared that the origin of circadian rhythms can be exogenous in certain cases and endogenous in others. Since the work of Bünning on plant life, and that of Pittendrigh,1 Halberg,2 and Aschoff3 on animals and man, it is no longer possible to regard circadian rhythms, in particular, and biologic rhythms, in general, as having an exclusively exogenous origin, and, more precisely, as being acquired by each individual in each generation.The results of experimental research suggest that:At all levels of organization, rhythmic activity appears as one of the fundamental