TARPON SPRINGS, Fla. - As an electronic flash fires, Rick Hill issues instructions: "Hold it. A little more this way. Perfect. Hold it."

Mr. Hill is operating a digital camera. His friend David Hughes is manipulating a model on a metal table. The model is a three-pound fetal pig.

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Gregg Matthews for The New York Times

The program shows a pig fetus on a dissection table, with surgical instruments and marked with a laser beam crosshair.

 "Awesome," Mr. Hill said.

Mr. Hughes and Mr. Hill, both 37, spent a week dissecting the fetal pig in a makeshift lab attached to Mr. Hill's garage near Tampa, taking thousands of photos.

They then turned those images into a computer program that permits users - mostly high school students - to simulate the fetal pig dissection. Point-and-click versions of scalpels, scissors and even saws allow students to find, remove and examine organs without ever smelling formaldehyde. Hundreds of schools, which are already using software as an alternative to animal dissection will receive the fetal pig module later this month. Other companies including Biolab, Digital Frog and DryLab also offer dissection software.

Nearly a dozen states have laws or regulations requiring public schools to offer students such an option. Animal protection groups have lobbied against dissection and many students have decided that dissecting real animals is not for them.

Mr. Hill said that he and Mr. Hughes, whose six-year-old company is called Froguts, are "on the fence" about whether students should be required to dissect. "We're providing a tool for people to use if they want it," he said.

In 1999, Mr. Hill's stepdaughter, Erin, who was then 11, dissected a frog in school. "About a week later, when I asked her questions, she had a hard time describing the organs in detail," said Mr. Hill, then a high school science teacher. That got him thinking about how he might simulate the dissection experience, in a format that allows users to repeat procedures and then review what they have done - and, he said, "without wasting another batch of frogs."

The men are going for verisimilitude. When they decide to use a tiny rotary saw to remove the top portion of the pig's skull, they add a similar saw - in icon form - to the tool kit in their program.

"If there was a USB device that would let us simulate the smell," Mr. Hughes joked, "we'd use it."

The company sends to subscribing schools compact discs with virtual dissections of six organisms. The fetal pig will be the company's first mammal, and the two men are excited about it. They spent a day examining the animal's exterior, then skinning it.

"We want to do a neat job," Mr. Hughes said. Along the way, they "sexed" the pig, looking for a scrotum or genital papillae - and making notes so that students could repeat the procedure.

Of course, each organism is unique, Mr. Hughes said. One of the things students get out of actual dissections, he said, is the realization that the pig in front of them is different from any other pig. "Theirs will never look exactly like the one in the textbook."

That is lost with virtual dissection.

But for students who will not dissect, they say, there is more to gain than to lose from a computer simulation. "Teachers say, 'We've been looking for a way out of dissection, and you've given it to us,' " Mr. Hughes said.

Source: Bernstein, FA. "An On-Screen Alternative to Hands-On Dissection." The New York Times. Published: October 4, 2005 5-8-2006. http://www.nytimes.com/2005/10/04/science/04diss.html?ex=1286078400&en=90b58c0ef63e92a3&ei=5088&partner=rssnyt&emc=rss