Bloodletting was a pervasive medical practice that dates as far back as ancient Greece and continued well into the 19th century. Physicians like Hippocrates believed bad health could be attributed to a fluid imbalance, and recommended bloodletting to help reset the body's balance. So, why did bloodletting stick around so long? Stephanie Honchell Smith digs into its popularity and shortcomings. Lesson by Stephanie Honchell Smith, directed by Denys Spolitak.