Jascha Heifetz, 86, one of the great violinists of this century and an artist whose marvelous talent was evident even in his early appearances as a child prodigy, died Thursday at Cedars-Sinai Medical Center in Los Angeles.

Hospitalized since Oct. 16 for treatment of injuries received in a fall in his home in Beverly Hills, he had undergone brain surgery. The immediate cause of death was not reported.

In a remark that was typical of the tributes elicited by Mr. Heifetz's passing, Sir Yehudi Menuhin, the London conductor and violinist, said: "Few people would disagree that he was probably the greatest violinist in our age. I would like to say that he was my greatest inspiration. I used to have all his recordings and I tried to emulate him."

Mr. Heifetz was born in Vilna, Lithuania, then part of the Russian Empire. When he was 3, his father, a musician, began to teach him the violin. He first played in public when he was 4 and when he was 6 he played the Mendelssohn Violin Concerto at Kovno. When he was 10 he made his debut in St. Petersburg and the following year he played the Tchaikovsky Violin Concerto with the Berlin Philharmonic Orchestra. Appearances in Austria and Scandinavia followed.

With the onset of the Russian Revolution in 1917, Mr. Heifetz came to this country. Despite his youth and the disruptions of World War I, his reputation as a major new force in music had preceded him. On Oct. 17, 1917, he made his debut at Carnegie Hall in New York. His performance that night exceeded the advance notices.

Critics compared him to Fritz Kreisler, the leading virtuoso of the day, and to Nicolo Paganini, the legendary Italian violinist and composer of earlier times. Pitts Sanborn described him as "a modern miracle." Sigmund Spaeth wrote that "a tall Russian being with a mop of curly hair walked out on the stage of Carnegie Hall and made the ideal a reality." A third critic said, "The newcomer plays with a tone so tragical, so intoxicatingly sweet, that only the molten gold of Fritz Kreisler can be conjured in comparison."

The debut was the occasion of one of the well-loved stories of musical legend. Among the audience were the violinist Mischa Elman, himself a prodigy as a child, and the pianist Leopold Godowski. As the performance continued and the ovations increased, Elman became visibly uneasy. At length he turned to Godowski and said, "It's hot in here, isn't it?

To which Godowski replied, "Not for pianists."

Mr. Heifetz soon was able to command $2,250 a performance, a figure that made him the highest paid violinist in the world up to that time.

For the next half century he appeared in concert regularly in this country and elsewhere. Often he played under trying circumstances. He was in Ireland during the Sinn Fein uprisings in the early 1920s; in Japan during the earthquake of 1923; in Bombay two days after Mahatma Gandhi, the saintly leader of the Indian independence movement, had been arrested, and in Tientsin, China, in 1931 at the time the Japanese invaded Manchuria.

He also played in Latin America and Australia and in 1934 he made a sentimental journey back to Russia. During World War II he played for American troops in war zones.

Mr. Heifetz made numerous recordings and many of them remain available. In 1975, in fact, there appeared a six-volume anthology of various works he had recorded since first coming to this country. He frequently played chamber music, often with the great cellist Gregor Piatigorsky and Artur Rubinstein, the legendary pianist.

As interested in modern music as he was in the classics, Mr. Heifetz commissioned works by contemporary composers, including William Walton, Mario Castelnuovo-Tedesco and Louis Gruenberg. He transcribed a number of pieces for the violin, the best known of which is "Hora Staccato" by the Romanian composer Grigoras Dinicu.

He made four films in Hollywood. Under the pseudonym Jim Hoyle, he published several popular songs. One of them, "When You Make Love to Me (Don't Make Believe)," was a hit in 1946. He liked jazz and included his own arrangement of George Gershwin's "It Ain't Necessarily So" on some of his concert programs, including a memorable performance which was filmed for television in 1971. He detested rock 'n' roll, asserting that "it's chief quality is noise."

Although he had not performed in public since the early 1970s, Mr. Heifetz continued a full teaching schedule until quite recently. He taught a master's class through the Extension Division of the University of California at Los Angeles and he also taught at the University of Southern California. Teaching, he said, was a duty.

"My old professor put his finger on me," he said. "He said that some day I would be good enough to teach. Violin playing is a perishable art. It must be passed on as a personal skill. Otherwise it is lost."

As long as he played in public Mr. Heifetz, unlike some other great performers, remained the master of his instrument and his music, apparently immune to the infirmities of age. Reviewing the 1971 television program, Paul Hume, the music critic emeritus of The Washington Post, had this to say about his reading of the Bach "Chaconne:"

"It was an immaculate, deeply personal, and strongly felt performance with fantastic, indeed, flawless, projection. At 70 Heifetz has not altered those musical tastes which have always marked his playing of this music. There are pauses other violinists avoid, but the architecture of the music and its very intent was totally exposed and expounded. To be capable of such an achievment is given to few mortals."

As a stage presence, Mr. Heifetz was correct, impeccable, unsmiling even when acknowledging applause. He held his body still when he played and his face was turned toward his fingers. The impression audiences got was one of formidable coldness and some critics found this quality reflected in his playing: more technical skill, on occasion, than feeling for the work at hand.

But Brooks Smith, his accompanist for 20 years, maintained that while the maestro's bearing might have put some people off, it was only necessary to listen to the music to find out "how very much involved" he was in it.

Nonetheless, there were difficult aspects of Mr. Heifetz's life. He enjoyed tennis, Ping-Pong and parties in his younger years, but he had few close friends. A citizen of the United States since 1925 and a resident of Southern California since 1930, he sometimes said his life in this country was too easy. "It worries me that we are soft," he said in one of his rare interviews. "There's little chance to think, to dream, to be original. It is a difficult place for creative work -- and I mean work. Everything is within reach."

A hard worker himself, he also could be stubborn. In 1953, during a tour of Israel, he was asked not to play works by Richard Strauss, a German composer much admired by the Nazis, because some survivors of the Holocaust found Strauss offensive. A Jew himself, Mr. Heifetz did so anyway, declaring that politics have no place in artistic considerations. This provoked an Israeli to attack him with a iron pipe. He was struck on the right hand but not seriously injured.

As the years advanced, Mr. Heifetz became more and more reclusive. When he went to the hospital in October he registered under the name Jim Hoyle, the alias of his pop music activities.

His marriages to actress Florence Vidor and Frances Speigelberg ended in divorce. Survivors include two children by his first marriage, Josepha and Robert, and one by the second, Joseph, who is known as Jay.

When the violin virtuoso Isaac Stern heard that Mr. Heifetz had died he said: "Since his debut in the United States he wa the most powerful force in violin playing in the world. He has been the inner ear of every violinist since at least 1930."

AMELIA M. ERDELY, 76, a resident of Arlington since 1961, died of cancer Dec. 9 at Arlington Hospital.

Mrs. Erdely was born in Fayette City, Pa., and lived there until she moved to Arlington.

Her husband, Julius Erdely, died in 1961.

Survivors include two daughters, Rita Vickers of Arlington and Regina Gore of Wills Point, Tex., and four grandchildren.

BERNARD H. BARNETT, 71, a senior partner in the law firm of Barnett & Alagia who also had been active in business in Louisville and Israel, died Dec. 10 at Emory University Hospital in Atlanta of complications following heart surgery.

Mr. Barnett, who lived in Washington and Palm Beach, was a cofounder of the law firm in Louisville in 1974. It now operates in eight cities, including Washington, and it specializes in national and international tax and business matters.

During the 1950s and 1960s he had been active in the development of an oil industry in Israel, and during the 1960s he helped develop a petrochemical industry there.

Mr. Barnett was a founder of the Louisville-based conglomerate National Industries, which merged with Fuqua Industries, and he had been a director of Fuqua.

He was also a former board member of the John F. Kennedy Center for the Performing Arts in Washington and a national chairman of the United Jewish Appeal. Mr. Barnett had also been a Republican Party fund raiser.

He was born in Helena, Ark., and graduated from the University of Michigan. He received his law degree from Vanderbilt University.

He moved to Washington in the late 1970s.

Survivors include his wife, Marian S. Barnett of Palm Beach and Washington; one son, Charles D. Barnett of Palm Beach; two stepsons, Jean S. Friedberg of Columbia, Md., and Howard A. Friedberg of Cleveland, and four grandchildren.