Jennifer Brown, a Chowchila kidnapping victim who said she is nine and amended it moments later to 10, testified yesterday about the lack of air in the cave in which she and 25 other children and their bus driver were once entombed.

Sitting in a chair too large, with her feet dangling six inches from the floor, she said the air "started to disappear. It started to get hard to breathe."

She was asked how she knew the air was disappearing, "Because Irene Carrejo (a 13-year-old kidnapping victim) told me it was."

When the underground roof looked like it was falling in, the prim and poised little girl remembered, "all I thought was the whole thing was going to cave in and we'd be squished."

A number of parents and a somber parade of nervous and often fidgeting children described the hours of July 15 and 16, 1976. When they were kidnaped by three armed men, held in vans in which they rode around for 12 hours and then hidden underground in a quarry for another 15 hours.

They were testifying in a small oak paneled Alameda County courtroom before Superior Court Judge Leo Deegan, who must determine whether any of the victims suffered bodily harm. If he finds they have, the trhree already convicted kidnapers, Fred Woods, 26, James Schoenfeld, 26, and his brother Rick, 23, will be imprisoned for life without the possibility of parole.

The children spoke in high-pitched whispers about fainting, nose bleeds, scratches, bruises and the stomach aches they suffered while held captive in what they call "the hole."

Testimony of nightmares, phobias and other psychiatric side effects of the adbuction has been excluded by the judge because the Chowchilla parents refused to have their children examined by defense psychiatrists.

In simple, halting terms the children remembered.

Cynthia Van Hoff, nine, snided nervously and remembered when Jennifer Brown was "singing 'If you're happy and you know it clap you hands.'"

"What happened when Jennifer was singing?" asked Alameda County Assistant District Attorney Joanne Parrilli, "Nobody clapped," Cynthia replied, tigging at her fingernails.

Other children testified that they lost 10 pounds during the 27-hour or deal, one complained of urination problems months afterwards another of shorlived car problems.

Tom Van Hoff, a Chowchilla farm worker and the father of nine-year-old Cynthia, said that when she returned home "she didn't have a word to say.

"Sge was ashamed of herself and what happened to her."

He said "she just throwed her arms around my neck and clung to me. She didn't say a word. She kept her head buried in my shoulders."

Joan Brown, a legal secretary and the mother of Jennifer, told the judge that when she finally saw her daughter, "she didn't even show a sign of recognition at all. I knelt down to put my arms around her . . . she had no expression. It was completely blank. It was like she was sleepwalking . . .

While the children testified about their fears and their beliefs that they would be killed. Woods and the two Schoenfelds - one time Eagle Scouts who never smoked and never drank - sat expressionless at the defense table 15 feet away.

The trial is expected to continue through this week.