"Most people," says Dr. Barbara Sonies, "take their tongues for granted." Yet, she adds, from the moment of birth, the tongue is ready to work. When a newborn lets out its first cry, the wail is formed by the tongue, and then, thanks also to the tiny tongue, a sucking motion marks the baby's instinctive search for mother's milk.

Animals' tongues may look like ours, says Sonies, but they and their associated central nervous systems and airways are not so versatile. Animals' tongues can support sucking and swallowing but can produce only a few primitive vowel-like sounds.

The tongue's resourcefulness is obvious to anyone who has been to the dentist. When the dentist numbs your mouth, says Sonies, "your tongue feels like a ball of cotton and you don't know where it is, but you still can speak. The tongue finds ways to compensate despite its lack of sensation."

Sonies has been studying the subtleties of tongue movements for more than a decade. She has looked at how the tongue works not only in people whose tongues work well but also in those whose tongues do not.

In 1977, she was working with a patient who had suddenly lost the ability to move his tongue, speak, and swallow properly. Sonies developed a procedure that allowed her to watch and analyze the patient's tongue movements and help him relearn how to talk and eat. Sonies has since refined the technology, and she has used it to monitor the actions of the tongues of many people.

The procedure relies on ultrasound imagery. A small transducer is positioned under the subject's chin; it sends signals and records images of the tongue, pharynx, floor of the mouth, and other structures as the person tries to swallow or talk. The movements are projected onto a video screen, and the patient can watch what is happening and, with the help of a speech pathologist, learn to imitate movements that will compensate for and correct some of the problems.

The pictures track tongue movements in "real time." They show that when someone talks, for example, the tongue moves back and forth and up and down, and its surface contours change. When a person eats and swallows, the tongue rotates from side to side and moves in various other ways.

The movements of the tongue for swallowing are remarkably similar from person to person. Swallowing begins when a ball of food -- the technical term is a "bolus" -- forms in the front of the mouth. A swift action of the tongue pushes the bolus to the back of the mouth; this happens in 1.2-1.5 seconds. Everything then switches to automatic pilot. The bolus can no longer be spit out as it could when it was still in the front of the mouth. The larynx moves up, the epiglottis moves down, the hyoid bone and tongue move to new positions, and the bolus journeys through the pharynx down to the esophagus, helped along by a combination of muscle contractions and gravity. In 8-10 seconds, the food passes through the esophagus into the stomach.

Swallowing is such an innate process that people who develop problems can often relearn to swallow: they watch and imitate videos of the process in someone else and their efforts are guided by a speech pathologist.

But speech is a different story. Speech is so variable that therapy for speech disorders must be individualized. A patient must try and try to make a sound; the right sound may emerge only after many false tries. What the pathologist does, says Sonies, is "show patients on ultrasound what they did to make the sound happen."

Speech pathologists work with their patients to produce and differentiate simple sounds, like bah and pah. When those skills are mastered, the patient can advance to more complicated sounds and even sometimes to such tricky tongue twisters as "which wristwatches are Swiss wristwatches?" that challenge even the most skillful speakers. The tongue, larynx or "voice box," and airways work together to generate meaningful sounds, but it is the brain that conjures up the words a person wishes to say.

Sonies says that safety is one of the real beauties of the ultrasound technology. Patients are not exposed to harmful x-rays nor do they have to swallow foods that have dangerous radioactive labels attached to them. Other techniques that monitor tongue movements and the later steps of the swallowing process -- x-rays, videofluoroscopy, and nuclear medicine procedures, such as scintigraphy -- have these disadvantages and can only be used in a limited way and for selected studies.

Tongues don't always work the way they are supposed to, and the nature of a tongue malfunction can sometimes help in the diagnosis of a disease or condition.

Sonies' early non-speaking patient, for example, had a rare disease called Steele-Richardson, which sometimes includes an abrupt distinctive change in tongue functioning. Strokes also often interfere with speech functioning. "A stroke patient," says Sonies, "may be unable to move the tongue from side to side." And, patients with Lou Gehrig's disease "have tongues that are like jello." In AIDS patients, dark purple spots sometimes appear on the tongue and throat, signs that the AIDS-associated form of cancer, called Kaposi's sarcoma, is present. Thrush and other infectious fungal diseases can be diagnosed definitively by looking at the patient's tongue to see if it has a white or green covering.

Sonies has worked with a number of patients who had polio as children, recovered, and were fine for several decades but, later in life, developed "post polio syndrome." These people have, among other problems, trouble swallowing. Their original bout with polio damaged many of their nerve cells but left others intact. The healthy cells compensated for those that were lost, but, with the passage of time, they too deteriorated along with associated muscles and tissues (1).

Sonies says that occasionally some really dramatic tongue abnormalities occur. For example, once in a while, a child will be born without a tongue. This is "very, very, very, very, very, very rare," she says, but, when it happens, surgeons take tissue from other muscles and try to build a soft artificial tongue.

What is more common, but still very rare, says Sonies, is for a child to be born with a huge tongue, "one that may hang out to the chin or even reach the tip of the nose." Surgeons can treat this condition, known as Beckwith-Wiedemann syndrome, by trimming the tongue to fit the mouth when and if it becomes obvious that the jaw will not eventually expand enough to accommodate the tongue.

Tumors will sometimes destroy part or all of a person's tongue. Most often, says Sonies, this occurs in people who smoke and drink alcohol. In some patients, the mouth can be fitted with a rubberized or hardened plastic artificial tongue that is attached like a retainer over the teeth. A grooved structure hangs down and helps the person eat and make sounds.

Barring disease, the fitness and actions of a person's tongue change little over a lifetime. "People," says Sonies, "may change their food preferences from pablum to shish kebob," but they do not alter the way that they swallow. The most notable change, she adds, is that as one ages eating may take longer. But that seems a minor inconvenience to swallow.

1. NEJM, 1991, 324(17):1162-1167.