Approximately 80% of those were from African Americans. In addition to being the majority of cadavers, many Southern teaching hospitals would only perform new live surgical techniques and demonstrations on African-American patients. Don't you know white men taught them all that about ghosts? That was a way of keeping them down, keeping them under control. There is a long history of whites using the supernatural to intimidate African Americans. During the slavery era, slave masters dressed as ghosts, rode around black communities on horseback. Later there were patrols called patterollers. After the Civil War, the Ku Klux Klan continued the "Night Rider" tradition. It was finally taken up by the Night Doctors. Between the Civil War and the 1930s, labour agents were sent by Northern employers to recruit African Americans from the South. In addition to restrictive laws, Southern employers used rumour to intimidate the workforce into staying in the South. One of the most popular rumours concerned doctors roaming Northern streets nightly, killing African Americans for dissection purposes. White Southern employers would also maraude around black communities in white gowns, further spreading fear, anxiety and unease throughout neighbourhoods already overburdened with anguish. New Orleans had an interesting variation on the Night Doctors called the "Needle Men". Thought to be medical students from Charity Hospital (now the Medical Center of Louisiana at New Orleans), the eponymous Needle Men, would poke unsuspecting individuals in the arm, resulting in death. Several explanations have been suggested, such as epilepsy and the 1924 case of a man who would poke women with a bayonet. I sure don't go out much at this time of year. You take a chance just walkin' on the streets. Them Needle Men's is everywhere. They always comes 'round in the fall, and they're 'round to about March. You see, them Needle Mens is medical students from the Charity Hospital tryin' to git your body to work on. That's 'cause stiffs are very scarce at this time of the year. Students at Charity Hospital were also referred to as "Black Bottle Men". The black bottle would be a poison given upon entrance to Charity Hospital, and the resulting death would allow dissection. It is now thought that the black bottle referred to cascara (Rhamnus purshiana) mixed with milk of magnesia, a laxative commonly given to admitted patients of the era. Charity Hospital did not have sole responsibility for "Needle Men" or "Black Bottle Men." Johns Hopkins Hospital was believed to be another source.