To this very day this sinew is extracted from the hind quarters
of all animals before it is allowable for a Jew to eat them.
This operation, in popular parlance, is termed porging.
The mysteries of the law are not to be communicated except to those who
possess the faculties of these five in combination:--"The captain of
fifty, and the honorable man, and the counselor, and the cunning
artificer, and the eloquent orator" (see Isa. iii. 3).
THE TALMUD, _Chaggigah_, fol. 13, col. 1.