Final answer:
Handwashing introduced by Ignaz Semmelweis in 1847 helped demonstrate that substances such as bacteria may cause diseases, later endorsed by Joseph Lister's use of carbolic acid, underlining the importance of hygiene in disease prevention.
Step-by-step explanation:
In 1847, a scientist noted that handwashing by physicians before patient contact resulted in reduced infection rates. This observation provided one of the first clues that substances such as bacteria may cause diseases. Hungarian physician Ignaz Semmelweis, observing high maternal mortality rates from puerperal fever, hypothesized that doctors were transferring infectious agents to patients. He mandated handwashing with chlorinated lime water, leading to a significant decrease in mortality rates.
Later, British surgeon Joseph Lister, informed by Semmelweis and Pasteur's work, incorporated handwashing and used carbolic acid as a disinfectant during surgeries, dramatically reducing post-surgical infections. This historical evolution in medical practice helps us understand the crucial role of hygiene and asepsis in preventing disease transmission, which is now a standard medical procedure.
Handwashing remains the single most important defense against the spread of many pathogens, and its effectiveness in healthcare settings underscores the significance of recognizing and controlling the routes of microbial transmission.