Johnny Sheffield, the former child actor who played Boy in the
Tarzan movie series starring Johnny Weissmuller in the late
1930s and '40s and later starred in the Bomba, the Jungle Boy
film series, has died. He was 79.  Sheffield died Friday of a
heart attack at his home in Chula Vista about four hours after
he fell off a ladder while pruning a palm tree, said his wife,
Patty.   The son of British actor Reginald Sheffield was 7 when
his father saw an advertisement in the Hollywood Reporter that
asked, "Do you have a Tarzan Jr. in your backyard?"   Sheffield,
who had appeared in "On Borrowed Time" on Broadway in 1938,
recalled in a 1997 Times interview that there were two parts in
testing for the role of Boy.    "He jumped into the deep end of
the swimming pool," Sheffield told The Times in 1997. "He knew I
couldn't swim. He said, 'Jump in.' I jumped in the deep end and
he took my arm and set me on his knee. He said, 'You're doing
fine. Hold your breath, we're going under.'   From 1939 to 1947,
Johnny Sheffiel