To honor Douglas Wilson, this paper reviews evidence for studying and quantifying rhythms as the indispensable control, whether to assess the effect of a fixed-calorie meal taken as breakfast or dinner, or to understand how human physiology and pathology may be affected by space-terrestrial weather. Since D. Wilson's work has dealt intensively with salivary hormonal determinations, we illustrate what can be learned from longitudinal series obtained in health or from a patient suffering from

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... amic depression episodes recurring twice a year and lasting 2-3 months. The socially less unacceptable collection of serial salivary samples should be introduced more broadly into laboratory medicine for a more refined diagnosis and as a means to guide the optimization of any needed treatment by timing.