Bloodletting in 1860, One Of Only Three Known Photographs Of The Procedure
In eighteenth- and nineteenth-century America, many symptoms of illness were believed to be caused by an excess of blood: the removal of some was therefore thought to alleviate the condition. There were two main methods of bloodletting: using leeches and venesection (i.e. cutting open a vein).  Bloodletting is achieved by fleams, scarificators, cupping glasses, leeches, and assorted instruments.   
If you search for ‘bloodletting’ in the Medical and Surgical History of the War of the Rebellion not that much shows up.  However if you search for ‘venesection’, then many citations pro and con as well as actual cases are found.
Bloodletting or venesection was practiced through out the Civil War, because when the War started, bleeding was an accepted practice in the medical community.  As the war progressed, evidence based treatment was leaning against the use of bleeding for various medical or surgical problems as reported in the Medical and Surgical History.
Source: Bloodletting (Venesection) During the Civil War By Dr. Michael Echols, Photograph WIKI

Bloodletting in 1860, One Of Only Three Known Photographs Of The Procedure

In eighteenth- and nineteenth-century America, many symptoms of illness were believed to be caused by an excess of blood: the removal of some was therefore thought to alleviate the condition. There were two main methods of bloodletting: using leeches and venesection (i.e. cutting open a vein).  Bloodletting is achieved by fleams, scarificators, cupping glasses, leeches, and assorted instruments.   

If you search for ‘bloodletting’ in the Medical and Surgical History of the War of the Rebellion not that much shows up.  However if you search for ‘venesection’, then many citations pro and con as well as actual cases are found.

Bloodletting or venesection was practiced through out the Civil War, because when the War started, bleeding was an accepted practice in the medical community.  As the war progressed, evidence based treatment was leaning against the use of bleeding for various medical or surgical problems as reported in the Medical and Surgical History.

Source: Bloodletting (Venesection) During the Civil War By Dr. Michael Echols, Photograph WIKI