Serfs were, essentially, the servant or commoner class. Often a serf would serve under a baron or lord who managed a fief (an area of land assigned to that lord by the king for management and protection). Serfs could be farmers, tradesmen, or servants to the gentry (nobility). Being a servant was the highest rank that could be achieved by a serf, unless one could conduct themselves well in battle and earn a knighthood.

The druids were an integral part of early Briton pagan religious practice. They were both healers and in their own way, preachers. While the Druids did use stone sites like Stonehenge for their religious practices, opposed to popular belief the Druids are not responsible for Stonehenge's creation.

Thanes, sometimes called earls, were the noble/ruling class before the establishment of one king in Britain with a house of lords underneath him. While Earls was as one of the answers it was not the correct popular name for them at the time. Thanes were only called earls in one area of early Britain, called Kent. 

Cholera proved to be one of the largest problems of the rapid urbanization and industrialization of the nineteenth century. Its spread was kept unchecked for two different but related reasons: its prevalence among the working poor and the incorrect beleif about its method of spreading. Most medical authorities of the time insisted it was caused by foul-smelling air in cities rather than the contaminated water supplies that actually spread cholera.

Edwin Chadwick is a well-known British social reformer who was active during the Industrial Revolution. Among other achievements, he is credited with helping pass the Public Health Act of 1848. Chadwick was concerned with the social well-being of the poor in British cities, in particular with the sanitation and public health of factory life.

Cholera is an extremely deadly disease that was prevalent in urban European society during the nineteenth and early twentieth centuries. It is spread through contaminated water and causes death through dehydration. The disease, like many diseases, disproportionately targets the poor and those without access to clean water. Studies of the disease led to improvements in public health, sanitation, and water treatments. The disease is now mostly eradicated in the Western world, but continues to routinely devastate parts of the developing world.

Despite being excluded from guilds and universities, the majority of caregivers in the Middle Ages were women, in particular family members and domestic servants of families.

Joseph Lister was a British surgeon in the nineteenth century who pioneered antiseptic surgery and greatly improved the safety and survival rate of surgeries. He expanded upon Louis Pasteur's ideas on “germ theory,” applying Pasteur’s theories to surgery and hospital experiences.

Edward Jenner developed the first smallpox vaccine in 1798. His revelation rested on an observation that milkmaids who had caught cowpox did not ever contract the far more virulent and deleterious smallpox. So, Jenner started inoculating test subjects with cowpox and determined that it worked as a vaccine against smallpox. This invention would dramatically alter life for European people and contributed to the skyrocketing population growth of the next two centuries.

Microorganisms were observed for the first time in the seventeenth century by the Dutch scientist Antonie van Leeuwenhoek. This opened up the world of the microscopic to doctors and medical scientists for the first time and would eventually contribute to massive advancements in medical understanding and practice.