What does "comma" mean?

Comma: (Mus.) A small interval (the difference beyween a major and minor half step), seldom used except by tuners. Comma bacillus (Physiol.), a variety of bacillus shaped like a comma, found in the intestines of patients suffering from cholera. It is considered by some as having a special relation to the disease; -- called also cholera bacillus. -- Comma butterfly (Zoöl.), an American butterfly (Grapta comma), having a white comma-shaped marking on the under side of the wings.