2 Dentists Say They’ve Found New Muscle

Forget the new form of matter discovered last year, or the new phylum of organisms found on lobster mouth parts, or the new planets recently sighted in our galaxy. Would you believe a new part of the human body has been found right under our noses?

Actually, right behind our eyes. Which may explain why it wasn’t noticed before.

That is, if it really wasn’t noticed before.

Two dentists in Baltimore believe they have found a “previously undescribed” structure of human anatomy--a muscle about 1 1/2 inches long that runs from behind the eye socket to the inside of the jawbone. It appears to assist in chewing. It has been found in every body in which they’ve looked.

“We kept saying this can’t be undescribed--it’s too large,” said Gary D. Hack, who teaches at the dental school at the University of Maryland at Baltimore. “Plus we said we’re dentists, not anatomists. Let’s go back to the [anatomical] literature and try to find it.”

So far, however, neither Hack nor Gwendolyn Dunn, a colleague at the dental school, has found any mention of the muscle in anatomy books. A small part of the structure appears in some drawings, but no text describes its full length, or its relationship to neighboring bones, nerves and blood vessels. They will present their finding today at the American Assn. for the Advancement of Science meeting in Baltimore.

Gross anatomy, the study of body structures seen with the naked eye, is not a big field of medical research. There’s a vein in the head named for Galen, a Greek physician who lived in the 2nd century. The greatest anatomist, Andreas Vesalius, died in 1564. There have been anatomical discoveries this century, but most have been blood vessels, connective tissue bridges and other small structures. Finding an overlooked muscle in the head is like finding an overlooked elephant in the living room.

“I would be highly doubtful,” said Michael Gershon, president of the American Assn. of Anatomists and a professor at Columbia University’s College of Physicians and Surgeons. “That’s the kind of thing that would really need scientific confirmation. But by no means would I say it’s not possible. That would be dumb.”

Gershon knows something about this. In 1990, he described the function of nerves running from the stomach and small intestine to other organs of digestion. They had been seen and illustrated in the 1800s, and then basically forgotten. Gershon looked at them anew and determined they formed the basis of an independent, gut-based nervous system. The discovery is leading to new insights in physiology.

For muscles, there are five identifying characteristics--”origin” and “insertion” (the parts of bones to which the muscle’s two ends are attached); “innervation” (the nerve that makes the muscle work); “vascular supply” (the artery and vein that serve it); and function. Different muscles can share the same function, such as moving the jaw. But in general, a muscle must have the other four characteristics all to itself to be considered a unique anatomical structure.

Hack and Dunn, who teach anatomy to dental students, believe their discovery satisfies that requirement. But they don’t expect many people to agree with them.

“Anatomists are going to be very, very resistant to saying this is a new muscle,” Hack acknowledged.

In this era, anatomical dissection is almost always done by the book. Instruction manuals lead students step by step through a cadaver, telling them where to cut and what to see. The two dentists credit their discovery--if it turns out to be such--in part to the influence of Richard T. Koritzer, a 69-year-old Maryland dentist.

Koritzer believes in doing dissections from unorthodox angles.