Which of the following improvements contributed to decreased mortality rates in the 19th century?

The development of antiseptic techniques was pivotal in reducing mortality rates during the 19th century. Surgeons like Joseph Lister advocated for the use of antiseptics to prevent infections during and after surgical procedures. Prior to the implementation of these techniques, surgical outcomes were often marred by infections, as bacteria could easily enter open wounds. By promoting cleanliness, using sterilized instruments, and applying antiseptics such as phenol, Lister and others significantly lowered the incidence of postoperative infections, which was a major cause of death. This advancement not only enhanced surgical safety but also built trust in medical practices, leading to more surgeries being performed with lower associated risks.

In contrast, while blood transfusions, anaesthetics, and improved surgical tools made significant contributions to medical practices, they did not directly target the prevention of infections, which was a leading cause of mortality in surgical patients at the time. Blood transfusions were risky and not well understood initially, anaesthetics improved the comfort of surgery but did not prevent infection, and while better surgical tools facilitated operations, they did not address the critical issue of asepsis. Therefore, the emphasis on antiseptic techniques stands out as the key advancement for reducing mortality in that era.