Such a pitch presents an additional challenge to the hitter because it causes the ball to move atypically during its approach due to the altered wind-resistance and weight on one side of the ball.
Alternative names for the spitball are spitter, mud ball, shine ball and emery ball, although technically, an emery ball is one where the ball has been abraded in much the same way that the original cut ball had been physically cut.
Ed Walsh, however, is certainly responsible for popularizing it. Walsh dominated the American League from 1906-1912 primarily on the strength of his spitball, and pitchers around the league soon copied his spitball or invented their own trick pitch. Long Bob Ewing had one of the best in the majors. Long Bob was an intimidating sight at 6' 6" with a pitch that danced all the way to the plate. He had great speed and a puzzling drop curve. However it is illegal to throw today in a game.
The dramatic increase in the popularity of "freak deliveries" led to a great deal of controversy throughout the 1910s regarding the abolition of the spitball and related pitches. (In his autobiography, Ty Cobb wrote that such "freak pitches" "were outlawed when the owners greedily sold out to home runs." (Cobb, My Life in Baseball--The True Record with Al Stump (1961).)
In addition, there were many safety issues with the spitball, as at times pitchers would use tobacco spit from chewing tobacco as their spit. Many consider the death of Ray Chapman in 1920 partially as a result of the spitball, since Chapman could not see the ball coming before it struck him in the head, killing him.
As a result, the spitball was banned in two stages. In the winter of 1919-1920, managers voted to partially ban the spitball, allowing each team to designate at most two pitchers who would be permitted to legally throw spitballs. Then, following the 1920 season, the spitball was banned leaguewide, except for existing spitballers who were grandfathered in and allowed to keep throwing the pitch legally until they retired.
Seventeen existing spitballers were granted this exemption. Burleigh Grimes lasted the longest, retiring in 1934. The complete list: Doc Ayers (played through 1921); Ray Caldwell (1921); Stan Coveleski (1928); Bill Doak (1929); Phil Douglas (1922); Red Faber (1933); Dana Fillingim (1925); Ray Fisher (1920); Marv Goodwin (1934); Dutch Leonard (1925); Clarence Mitchell (1932); Jack Quinn (1933); Allen Russell (1925); Dick Rudolph (1927); Urban Shocker (1928); and Allen Sothoron (1926).
One of the most famous spitballers was Preacher Roe, who played for the Brooklyn Dodgers in the 1950s. Roe was renowned both for his ability to control the spitball, as well as to throw it without getting caught. Another famous user of the pitch was Gaylord Perry, who went so far as to title his autobiography Me and the Spitter. (For example, Gaylord would sniff red peppers to make his nose run or he would put vaseline on his zipper because umpires would never check there.) One sportswriter quipped that "Gaylord Perry's 3.67 ERA was more than he expectorated."