"Everything we observe in science shows us that mind and brain are inextricably woven together. We never see brain without mind and we never see mind without brain. That doesn't mean they are the same. They are irreducible realities coupled to each other."

-- A neurologist speaking in the final segment of "The Brain."

The brain. Gland? Muscle? Hardware? The computer people actually call it wetware. Have you heard that old "truism" that people lose 1,000 brain cells a day after the age of 25? Well rest easy -- it just isn't true. "And a good thing too," says a colleague. "I need every one I've got."

Of course some of the cells are gone with age, we are told, but generally that doesn't signify because, barring some catastrophic disorder, we make better use of what we've got. Rat brains grow larger in enriched environments -- at any age. Do human's? Probably. "A brain cell," say the scientists, "is a brain cell, whether rat or human."

But just what is it that we've got, anyway?

The eight-part WNET (New York PBS) series "The Brain" sets out to answer that question as well as anyone can -- which, as any neuroscientist will admit at the firing of a neuron, is not very well at all. Oh, better than before, of course, and better every day -- discoveries about the brain are exponential.

But still, that three or so pounds of gray matter and white matter that we carry around inside our skulls might unlock the secrets of our humanity, of who we really are, and of where our self-awareness comes from. It is the brain -- not space -- that is the true frontier.

No one knows that better than the folks who put together these eight one-hour programs, the first of which will be broadcast tonight at 8 on WETA.

For the past 3 1/2 (of the nearly five years the series has been in preparation) the series science editor and codeveloper has been Richard Hutton. A veteran science writer, mostly in genetics and orthopedics, Hutton describes himself as having become -- through his experiences on the series -- forever awed by the way his own brain is orchestrating his actions, his breathing, his gestures, his heartbeat, his awareness of his environment, not to mention his thinking at any given moment.

Hutton and his colleagues decided to organize the series according to two basic principles: Each program theme would be based on specific brain functions, and each would be told through human stories.

As a result, the series is coherent and dramatic; educational, of course, with auxiliary materials -- a text and study guides -- for a college level course that is being offered in more than 100 colleges and universities. But it is also accessible, and, for the most part, endlessly fascinating.

It is peopled with such as these:

*Phineas Gage (dramatized), a 19th-century railroad foreman who miraculously survived a freak accident in 1848 when a three-foot-long, 13-pound dynamite tamping rod was blown through his head. His personality underwent dramatic change -- from dependable, gentlemanly and likable to loud, profane, capricious and impulsive. Such changes demonstrate the role of the cerebral cortex in damping the more primitive "animal" brain. His skull and the rod are still preserved at Harvard. PCP, the animal tranquilizer sold as an illicit drug called angel dust, we learn, does today what Gage's rod did 150 years ago.

*Greg Louganis, the Olympic diver, who is, after all, not just a "hunk," but a perfect blend of brain and brawn, the brain via visual pathways directing the perfect dive at its most detailed level.

*Max Schmidt, an East German homosexual born during World War II, is part of a controversial experiment purporting to show that prenatal stresses on the mother may affect sexual differentiation of the brain of the offspring. One study shows that twice as many homosexuals were born in Germany during World War II as during the six years before and the six years after. Other studies do show that sex hormones may affect brain development. Left-handedness may be an example.

*Pat Moore, an Arlington woman whose seasonal depression has been eased by artificially lengthening her winter days by means of strong lights. She was one of the first successes in a study program at the National Institute of Mental Health.

*Tony, a 58-year-old carpenter who has some 50 different personalities living within him. His brain displays different patterns on imaging equipment depending on which personality is performing the tests. The tests were done in a unique program run by Dr. Frank Putnam of NIMH at St. Elizabeths Hospital. Says one specialist in multiples, "within one multiple there may be somebody who is a good writer, somebody who has skills in photography, somebody who is very good at numbers and somebody who . . . prefers music instead. I think it suggests that brains of non-multiples are capable of far more than we end up doing . . ."

*Jerry, a seriously afflicted schizophrenic. Off camera, Jerry provided one of the crew's most moving experiences. He had, Richard Hutton recalls, been generally hostile, even occasionally threatening during the weeks of filming. But the day the TV team was leaving, they found him "sitting in the dark listening to a Neil Diamond record," says Hutton. "He said, 'I'm gonna miss you guys.' One of the cameramen went up and said, 'give me a hug,' and he did. It was a powerful moment."

It is a powerful series.