Cook maintains the affable, easy-going manner of a natural athlete. He goes by the childhood nickname "Jimi" that his parents gave him. And he manages an easy rapport with his students, chatting and joking with them about music as diverse as U2 and Wayne Newton. His students say he's friendly, even "cool."

"He makes learning fun," says Andrea Klepzig, a fourth-year veterinary student from Farmington, Mo. "He views you as a colleague. He doesn't talk down to you. He challenges you every second you're with him."

And he is not above challenging himself. In 1996, while still a resident, Cook attended a scientific symposium in Orlando, Fla., where he learned about the amazing regenerative powers of pig gut. The material is a paper-thin collagen membrane called the submucosa that makes up the middle layer of a pig's small intestine.

The healing properties of small intestine submucosa, or SIS, were discovered by researchers at Purdue University who were trying it out as a vascular graft in dogs. The researchers suggested that submucosa may have evolved its abilities because the intestines must heal quickly from the constant insults of bad food, viruses and bacteria. SIS has stimulated a lot of interest in the medical community. It already has been approved by the FDA for use promoting healing of urinary bladders, injured rotator cuffs, burns and diabetic skin ulcers. Future applications could include mending arteries, the esophagus, even the intestines.

Purdue has licensed rights to all orthopedic uses of SIS to DePuy Orthopaedics Inc., an Indiana-based subsidiary of Johnson & Johnson. Cook says he was doubtful at first about SIS, so he asked researchers at the symposium for some of it that he could use to experiment. "I got the material just to prove that it wouldn't work," he says. "I'm a typical scientist. I'm very skeptical."

At the time, Cook was studying articular cartilage, the cartilage at the ends of long bones that can wear out and cause arthritis. He put some of these cartilage cells into a petri dish with the SIS to see what would happen. "Sure enough, the cells loved it and started making cartilage-like tissue," he says.

Researchers at MU and elsewhere are still studying how SIS works, but it appears that the tissue is a good biological scaffold that includes just the right combination of growth factors. It may well be a better mix than anything that could be concocted in a laboratory, Cook says. "We can synthesize all kinds of things, but I don't think we will ever be smarter than Mother Nature."