Sen. Robert C. Byrd has addressed hundreds of issues in his 49-year Senate career, but his speech Thursday was unusually personal.

It dealt with his own advanced age, tremors, slow gait and delegation of duties he once held close.

Byrd, 89, stood on the Senate floor to defend his energy and mental acuity, even as he acknowledged that aging takes a toll. The West Virginia Democrat said he wanted to respond to recent accounts of his Senate work, including a June 14 Associated Press article noting that aides or fellow senators sometimes prompt him to respond to colleagues' questions or remind him of their names.

"I may not like it," Byrd said of growing old, but "I will continue to do this work until this old body gives out. Just don't expect that to be anytime soon."

Byrd is the longest-serving senator in history, third person in the line of presidential succession, and chairman of the Senate Appropriations Committee. He has delegated some of the chairman's traditional duties to other members, saying Thursday: "I am sure that my younger colleagues ... appreciate the opportunity to play a larger role."

Shouldn't they "spread their wings," he asked, "while the old wise Byrd watches?"

Byrd made his speech just after the Senate completed a high-profile vote that essentially doomed a long-debated immigration bill. Several senators remained in the chamber, but most were buzzing about the vote and had to be hushed for Byrd to begin.

"My only adversity is age," Byrd said, reading from a text. "It is not a bar to my usefulness as a senator. I still look out for West Virginia. I still zealously guard the welfare of this nation and its Constitution. I still work, every day, to move the business of this nation forward, to end this reckless adventure in Iraq."

His hands shaking noticeably, Byrd acknowledged that his recent signature on a document, published in some newspapers, "looks like I signed it in a moving car. Some days, the benign essential tremor that I have had for years now is worse than on other days."

"It is annoying," he said, "but hardly evidence that I am at death's door."

An essential tremor is a fairly common neurological disease that causes a person to tremble most noticeably while active, but has less impact when at rest.

Byrd said Americans should be more accepting of old people and the changes that advanced age causes.

"In this Internet-savvy, media-infused culture," he said, "we have forgotten that people get older. Even, dare I say it, old.

"In a culture of Botox, wrinkle cream and hair dye," Byrd said, "we cannot imagine that becoming older is a good thing, an experience to look forward to and a state worthy of respect."