Michael J. Fox’s burning desire to find a cure for his debilitating Parkinson’s disease got a giant boost with the birth of his fourth child by wife Tracy Pollan.

Esme Annabelle arrived at 7 pounds, 6 ounces at a New York hospital on November 3, giving the 40-year-old actor further resolve in his struggle, say friends.

“Michael will never quit, no matter how long the search or how weakened his illness might eventually make him,” a co-star from his hit TV series “Spin City” told The ENQUIRER.

“He said: ‘I have a new life now, a two-part existence — spending time with my kids and loving them, and using every moment to help Parkinson’s research.’ “

Michael was at the hospital when 41-year-old Tracy gave birth, a source revealed.

“He was encouraging Tracy, who had a difficult time with this child.

“Tears of joy ran down his face when the nurse eventually handed him his new daughter and he rocked her gently in his arms.

“Tracy looked on fondly from the bed as Michael and Esme got acquainted for the first time.

“Michael told me before the birth, ‘Unless they find a cure, I won’t be in good shape before my fourth child’s a teenager. That thought shatters me, but it also makes me more determined than ever to do everything possible in search of that cure.’ “

Fox, 40, was diagnosed in 1991 with the crippling neurological disorder, but he kept it hidden from the public for seven years.

When he could no longer hide his tremors and jerky movements, he quit “Spin City” in May 2000 and started the Michael J. Fox Foundation for Parkinson’s Research.

“Michael is a brave risk-taker who will do whatever it takes to get better,” a friend declared.

“He was tormented earlier this year, when Tracy’s pregnancy was confirmed, about whether he should keep looking for experimental treatments or play it safe.

Fox is writing a book about his battle with Parkinson’s, “Lucky Man,” which is due out in April.

“His feeling was that if he does nothing, he’ll never be able to be a fully functioning dad for Esme, along with his 6-year-old twin daughters Aquinnah and Schuyler and his 12-year-old son Sam.

“Yet if he takes a big risk and it backfires, that could cripple him so badly that he’d never experience the joys of normal fatherhood.

“Michael’s attitude is to just keep pushing on — because sitting back and waiting for things to change won’t accomplish anything.”

When President Bush approved limited federal funding of embryonic stem cell research on August 10, Fox was quick to applaud — because cell replacement therapy shows great promise in attacking Parkinson’s disease.

Said a spokesman for his foundation: “Fox wholeheartedly believes that if there is a concentrated effort, researchers can pinpoint the cause of Parkinson’s and uncover a cure by 2010.”