During the Civil War
Doctors had started putting all those wounded and sick under diets. These diets were believed to help the body heal faster and help the patient become stronger to fight off any infection.
One of the first people who had gone under amputation was Daniel E. Sickles who was a major general. Within an hour of having his leg shattered, in the Battle of Gettysburg, it had already been cut off and amputated. This was the quickest way doctors started to treat soldiers who were wounded in battle.
Disease V.S. Combat Deaths
Poisons? Bad Air?
Doctors were not that knowledgeable about medicine yet at this time, so some things used to "treat" patients was lead and other things we have learned are poisons to us, this did not help death rates drop and they continued to climb as the "treatments" would kill patients. Doctors also believed that some disease was due to "bad air" such as gases we breathe. Massive bonfires would be held to help burn the "bad air". This was believed to have helped.
Most believe that hospitals in the Civil War weren't very clean or sanitary. Yet most hospitals were actually cleaned on schedules daily to try to help prevent infection or spread of any disease.
The Civil War in Four Minutes: Civil War Medicine
Death Count From Hospitals State Based
So What Medical Advancements Were Made?
Doctors learned the new technique of amputation, learning that it was the quickest way to remove any broken or damaged limbs. They also learned this help prevent infection as it was quicker to preform an amputation and get the next patient in rather than performing a full blown out surgery. Doctors learned a lot more about preventing disease and what was causing it, as lead and other things were found out to be poisonous and "bad air" was not the cause of most diseases. Rather it was the sharing of harmful bacteria.