* Using the tongue is less peculiar than it seems. Before doctors could ship patients’ bodily fluids off to labs for analysis, they sometimes relied on tongue and nose for diagnostic clues. Intensely sweet urine, for instance, indicates diabetes. Pus can be distinguished from mucus, wrote Dr. Samuel Cooper in his 1823 Dictionary of Practical Surgery, by its “sweetish mawkish” taste and a “smell peculiar to itself.” To the doctor who is still struggling with the distinction, perhaps because he has endeavored to learn surgery from a dictionary, Cooper offers this: “Pus sinks in water; mucus floats.”
* The shipping of bodily fluids was a trying business in the 1800s. One shipment to Europe took four months. Bottles would arrived “spilt” or “spoilt” or both. One correspondent, taking no chances, directed Beaumont to ship the secretions “in a Lynch & Clark’s pint Congress water bottle, carefully marked, sealed and capped with strong leather and twine, cased in tin, with the lid soldered on.”
6
Spit Gets a Polish
SOMEONE OUGHT TO BOTTLE THE STUFF
ERIKA SILLETTI STUDIES saliva in a sunny top-floor lab in the Dutch town of Wageningen. A Gaudi poster hangs on one wall, and the windows look recently washed. The day I arrive, she wears a tailored wool skirt, short but not overly so, black leather boots, and a dove-gray cashmere sweater. If you saw a picture of Silletti in a magazine, you might make yourself feel better by assuming that the creamy skin tone and flawless symmetry of her features had been photoshopped. Only one thing fits my imagined notion of what saliva science looks like: a two-foot-tall, freestanding steel paper-towel holder with the fattest roll of paper towels I’ve ever seen.
I came upon Erika Silletti while roaming the abstracts of a dental conference. She later told me the presentation she gave there was met with blank looks. “They think of it as lubricating, and that’s it!” She went back to her hotel room and called her boyfriend in tears.
It is safe to say that no one in this world understands and appreciates saliva like Erika Silletti.*
HUMANS SECRETE TWO kinds of saliva, stimulated and unstimulated, no more alike than most siblings. The prettier child is stimulated saliva. It comes from the parotid glands, between cheek and ear. When a plate of Erika Silletti’s spaghetti carbonara makes your mouth water, that’s stimulated saliva. It makes up 70 to 90 percent of the two to three pints of saliva each of us generates daily.
We’re going to gather some now. Silletti pulls on a pair of blue latex gloves that so pleasingly complement the gray of her sweater that they look like part of the ensemble. She picks up two stoppered plastic vials. Inside each is a second, smaller vial, which contains a tightly compressed, cylindrical cotton wad. This is the Salivette saliva collection system. Silletti uncaps a Sharpie and marks an M, for Mary, on one, and an E on the other.
The Salivette instructions are printed in six languages. Erika Silletti, born in Italy, fluent in English, living in the Netherlands, can read three. “Kauw dan 1 minuut lichtjes op de wattenrol.” “Masticate delicatamente il tampone per un minuto.” “Gently chew the tampon for one minute.” This is the simplest way to collect stimulated saliva without also collecting the food that stimulated it: you chew the collection device. This is “mechanical stimulation” (as opposed to gustatory or olfactory stimulation, which we’ll come to). Il tampone will wick our flow, and then Silletti will place each back in its vial and put them in a centrifuge. The liquid will be spun from the cotton and flow down through an opening at the bottom of the inner vial, ending up in the outer vial.
The Salivette makes an unmistakable point: your parotid glands don’t care what you chew. There is nothing remotely foodlike about superabsorbent cotton, yet the parotids gamely set to work. They are your faithful servants. Whatever you decide to eat, boss, I will help you get it down.