Exogenous Timing of Rat Spontaneous Activity Periods.

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Abstract
Periods of spontaneous running of a male white rat in constant conditions of light and temperature for 60 days, except for 6 or 7 brief, irregular periods of darkness, and irregular occasional times of replenishing the water and food supply, were monitored continuously. Precise periodisms of 2 frequencies, solar-day (24 hr.) and lunar-day (24.8 hr.)were evident in the data and persisted throughout the study. The larger amplitude was the lunar-day with lunar "midnight" maximum and "noon" minimum. The solar-day periodisms were transient activity periods occurring at different hours of the solar-day, each continuing for a few days before disappearing, and being replaced by new ones. Reasons for believing the periods exogenous are presented and a role of these in the generation of commonly present activity-rhythms of unnatural periods through autophasing phenomena is postulated.