Ocean; Fetus; Metabolism; Geology; Taste; Religion; Alchemy; Cure: These are just some of the chapter headings in Tisdale's book about salt--an old-fashioned discursive essay too wide-ranging to have any kind of theses. A nurse whose earlier books have criticized modern hospitals (The Sorcerer's Apprentice, 1986) and profiled a nursing home (Harvest Moon, 1987), Tisdale demonstrates an understanding of physiological functions; but her interest is more in atmospheric musing than in scientific explanation. Her prose can be felicitious (""The original purpose of taste is survival: to know with a single sip or lick whether a food is edible or toxic, nourishing or deadly, out of the enormous range of sensations the world of. lets""), but she sometimes whips it up to a froth unbalanced by any weight of thought. (""There is no salt in the ocean. Dash, splash, wave on wave and the sportive fingers of spindrift between your toes; no salt""; about blood pressure, she writes ""High blood pressure is a jam-packed cultural fault, a slang of lifestyle and desire, a debt being paid""). In the end, Tisdale flutters over a lot of surface, spewing data with flash and dazzle, but never engages readers in any deep digging or challenging speculation.