... are repeated, the series is divided by commas. The comma stands for, in effect, the word and . The comma before the final item, before and , is often optional, but it is used here to make clear ... after-the-fact, and largely ineffective,chemical prophylaxis. Simple and to the point. Now consider the same sentence, taking advantage of opportunities to provide additional information and to expand ... of the civil right movement. It was lucky for David Halberstam, for the civil rights movement, and for all of us that Halberstam became a reporter for the Nashville Tennessean in 1956. Just...