How did people transfuse blood in 1800?

Blood transfusion as a medical procedure dates back several centuries, but in the 1800s, the practices surrounding blood transfusions were quite different from what is considered medically sound by today's standards. While there were attempts at experimenting with the transfusion of blood between humans and animals, these efforts faced limitations and skepticism from most of the medical community. Blood transfusion between humans only started gaining real scientific attention and traction towards the early 1900s thanks to advances in understanding blood groups and serology.