Unlike, say, salamanders, starfish and flatworms, mammals do not possess the ability to regenerate limbs (or, in the case of worms, half their bodies). On the other hand, report researchers at the University of Southern California, humans appear capable of repairing large sections of their ribs.

The scientists came to this conclusion after monitoring the healing of a human rib, using CT scans, that had been partially removed by a surgeon. In six months, the patient's body partially repaired more than 3 inches of bone and almost a half-inch of missing cartilage.

When they explored further in mouse experiments, they found that missing ribs were repaired when the surrounding sheath of tissue, called the perichondrium, remained intact.

The findings may have significant implications.

"We believe that the development of this model in the mouse is important for making progress in the field of skeletal repair, where an acute clinical need is present for ameliorating skeletal injury, chronic osteoarthritis and the severe problems associated with reconstructive surgery," said Francesca Mariani, principal investigator in the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC.

Body of Knowledge

A person can expect to breathe in at least 45 pounds of dust over his or her lifetime.

Get Me That, Stat!

A single doorknob coated with viruses can contaminate up to 60 percent of people in a building in just four hours, reported University of Arizona researchers at a recent conferment on antimicrobial agents and chemotherapy.

Number Cruncher

An avocado burrito from El Pollo Loco (408 grams) contains 490 calories, 162 from fat. It has 18 grams of total fat, or 28 percent of the recommended total fat intake for a 2,000-calorie daily diet, according to the Calorie Count database.

It also contains 85 milligrams of cholesterol (28 percent), 1,340 milligrams of sodium (56 percent), 54 grams of total carbohydrates (18 percent), 11 grams of dietary fiber (44 percent), 6 grams of sugar and 34 grams of protein.

Counts

2.2: average number, in millions, of marriages each year in the United States.

6.8: marriage rate per 1,000 people in the U.S.

3.6: divorce rate per 1,000 people in the U.S.

Source: Centers for Disease Control and Prevention

Mania of the Week

Onychotillomania: compulsive picking of fingernails.

Never Say Diet

The speed-eating record for fried mushrooms is 11.5 pounds in eight minutes, held by Molly Schulyer. Warning: Most of these records are held by professional eaters; the rest are held by people who really should find something better to do.

Observation

"I tried every diet in the book. I tried some that weren't in the book. I tried eating the book. It tasted better than most of the diets." — entertainer Dolly Parton

Medical History

This week in 1855, French physiologist Claude Bernard announced the discovery that glycogen is stored in the human liver. Glycogen is a kind of animal starch. It can be readily converted into glucose, which the body's cells use to release energy. In this function, it acts as stored fuel for animals, just as starch is stored in plants.

Epitaphs

"Never Born. Never Died. Only Visited this Planet Earth between Dec 11 1931 — Jan 19 1990." — Indian mystic and guru Chandra Mohan Jain, otherwise known as Acharya Rajneesh, Bhagwan Shree Rajneesh and Osho. He famously founded a commune in Oregon in the 1980s and believed in the possibility of a permanent state of "superconsciousness."

To find out more about Scott LaFee and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.