Most of the modern forms of football are derived from ancient
games, especially harpaston and harpastrum, played in Greece and
Rome. These survive today in Tuscany and Florence under the name
calcio. Meanwhile a rugged, undisciplined type of football took
root in the Middle Ages in England, where despite royal edicts
banning the game from time to time, football remained popular
until the early 19th cent. Different forms of the game soon
developed at the various English public schools, including
Rugby, Eton, and Harrow. Eventually, two main games emerged. One
was primarily a kicking game, which later became association
football, or soccer; the other (dating from 1823) was football
as played at Rugby, in which carrying the ball and tackling were
permitted. The American game is played by two opposing teams of
eleven. The football field is level, measures 100 by 531/3 yd
(91.4 by 48.8 m), is marked off by latitudinal stripes every 5
yd (4.57 m) and has at each end an end zone 10 yd (9.14 m) deep.
In the center of