1915: Mack Sennett's Keystone Cops comedies are popular at the movies, featuring a large group of bungling policemen running around and creating mayhem.

1933: A string of movies about hard-boiled gangsters, including Little Caesar (1930), Public Enemy (1931), and Scarface (1932), has given policemen a sense of self-importance.

Today: The trend in police dramas is toward the collection of minute pieces of evidence, in direct contradiction to the brutish destruction wrought by the officers in "The Night the Ghost Got In."

1915: In the middle of World War I, many of the young men of Thurber's age are off in the trenches of Europe.

1933: In the middle of the Great Depression, many family members who would otherwise have gone their own way are still living at home, unable to afford separate housing.

Today: The past decade has brought a dramatic rise in the number of people moving back home after...