Ralph Waldo Emerson (1803-1882), perhaps best known for his essay Self-Reliance (1841), was one of America's most influential thinkers and writers. After graduating from Harvard Divinity School, he followed nine generations of his family into the ministry but practiced for only a few years.
The first menstrual period is called  menarche .. The menstrual cycle is about four weeks long, starting on the first day of bleeding and ending when the next period begins. However, it can vary greatly when a girl first starts her period. It may skip months or come several times per month in the beginning.
A Girl's First Period: A Regular Visit. When your first period finally arrives, don't be too worried if it doesn't stick around for long. It can sometimes take your body a few months or even a few years to get into a regular pattern. Periods usually come every 28 to 30 days and last for three to seven days.