ALKALINE TIDES1

Diurnal variations in urinary acidity have been described and investigated extensively since Bence Jones (1) first reported the excretion of alkaline urine after meals. This post-meal alkaline tide and the period of spontaneous alkalinity which begins in the early morning hours, the socalled morning alkaline tide, have received especial attention, and several hypotheses have been advanced to account for them. The subject has been reviewed recently by Brunton (2). The reported observations have been nearly all of serial determinations of acid concentration in the urine or of urinary pH, data which permit no estimation of the amount of alkali excreted or retained per unit time. The few papers which present quantitative data of acid excretion have used methods which to us seem faulty or inaccurate, or in the investigation of the morning alkaline tide have paid no attention to variations in urinary volumes or to exercise and change of posture, factors which may have a striking effect on the curve of acid excretion. We have therefore investigated the spontaneous morning alkaline tide as it occurs in the normal resting subject without food or water, and then have studied some of the effects produced by exercise, by variation in fluid intake, and by the ingestion of food.