Complex sentence: Liquid tobacco enemas were often given to ease the symptoms of a hernia, however by the early 19th century the practice fell into decline, when it was found that the principal active agent in tobacco smoke, nicotine, was poisonous.
Split into simpler sentences: Liquid tobacco enemas were often given to ease the symptoms of a hernia. During the early 19th century the practice fell into decline, when it was discovered that the principal active agent in tobacco smoke, nicotine, was poisonous.