Apis (Eg.), or Hapi-ankh. The “living deceased one” or Osiris incarnate in the sacred white Bull. Apis was the bull-god that, on reaching the age of twenty-eight, the age when Osiris was killed by Typhon—was put to death with great ceremony. It was not the Bull that was worshipped but the Osiridian symbol; just as Christians kneel now before the Lamb, the symbol of Jesus Christ, in their churches.
Source: H.P.Blavatsky - The Theosophical Glossary