ABSTRACT
The knowledge that the numerous biological functions and physiological activities-in human and many mammals (hibernation, etc.), birds (migratory behavior, etc.), and plants (¡owering, autumn fall leaves, etc.)—are subject to a temporary rhythmicity is as old as man himself. All living organisms are characterized by the presence of a cyclic rhythmicity in a wide variety of biological and behavioral processes. “Biological rhythms” are known as the recurrence of phenomenon within a biological system at regular intervals. These rhythms involve an adaptation to the environment.
