An Increasingly Complex Relationship Between Salt and Water

One hundred fifty years ago this year, physiologist Moritz Schiff proclaimed from a pulpit at the University of Florence that the sensation of thirst, rather than being secondary to dryness of the throat, is a "general sensation, stemming from lack of water in the blood." Expounding, he declared "the dryness of the throat that normally accompanies [thirst] is merely a secondary phenomenon, analogous to the weight of the eyelids that accompanies sleepiness."1 Fifty years later, Erich Leschke would demonstrate that intravenous infusion of hypertonic saline in humans provoked a "sudden and violent thirst."2 Subsequent studies revealed that increased dietary salt stimulates fluid consumption in experimental animals, and the role of increased oral fluid intake in mitigating dietary salt–induced hypertonicity while expanding extracellular fluid volume became established renal canon.

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