Just 15 minutes into Robert Altman's new movie "A Wedding," Lillian Gish, who plays the groom's grandmother, quietly expires in bed.

For the rest of the film's hectic two hours we get occasional glimpses of her as a remarkably happy-looking corpse, the focal point for the 43-odd characters Altman has caught carousing through a nightmarish wedding reception.

"A Wedding" is Gish's 100th movie. She started in the business in 1912, and appeared in such classics of the silent screen as D.W. Griffiths's "The Birth of a Nation," "Intolerance" and "Broken Blossoms."

In her comfortable Slutton Place apartment here, which she inherited from her mother, the veteran actress reminisced recently abouta distinguished career which - running from Griffith to Altman - spans all of movie history. The apartment, filled with family and professional mementos - including Oscar Gish won for no specific film but for a lifetime's achievement - is it self almost a movie museum.

What was it like to play a corpse in a very modern black comedy?

"I'd never seen an Altman film," Gish confessed, "But of course I'd heard all about him. He just called me one day and told me a bit of the story. He said I died in it, but it wasn't sad. This piqued my curiosity, so I agreed to make the film."

"A Wedding" was shot in sequence, so Gish's role took just a week of filming.

"Working with Altman was just like a long family picnic. He'd let you change lines and invent business, and made everyone feel at home on the set. His own children and everyone else's children came to see the rushes every evening, and we all had a grand time - it was very relaxed."

Sitting on a sofa festooned with petit-point pillows of Thurber dogs, Gish recalled some of the joys and hardships of the old days of film-making.

"There's a lot of talk now about people taking drugs on movie sets, but that just didn't happen then. You had to get up before dawn for a 12 hour day. Griffith had to rehearse the life out of you to make his movies quickly because he had so little money to work witty.

"Do you know there was only one take for each shot in "The Birth of a Nation? I was practically unconscious with flu during the rehearsals of 'Broken Blossoms' but I showed up anyway. It was shot in 18 days and nights. I saw it recently with a young audience, and still held up.

"Griffith worked harder than anyone else. he had no time for drugs because he had to have a clear head all the time. The whole movie was in his head - there was on script."