Surgery today is almost unrecognisable from the butchery that passed for healthcare many centuries ago.

When surgery was in its infancy, it was hampered by the fact that human anatomy was a mystery. With the church placing limits upon human dissection on religious grounds, doctors and surgeons instead had to rely on observations of animal anatomy.

Galen’s vivisections of animals were hugely influential. He was an important anatomist of ancient times, active in the second century.

He also served as a physician to gladiators, which allowed him to study all kinds of wounds without having to perform any human dissections.

Although some of his observations, particularly those concerning the purpose of arteries, were true, he also made many errors which would persist in medical belief for centuries.

For a long while, human dissection was thought unnecessary when all the knowledge about human bodies could be read about in texts from early authors such as Galen.

Leonardo da Vinci, primarily an artist and inventor, was also trained in anatomy. In 1489, he began a series of anatomical drawings depicting skeletal structures, muscles and organs of humans and other vertebrates that he had dissected.

His surviving 750 drawings represent ground-breaking studies in anatomy. He dissected around 30 human specimens until, under order of Pope Leo X, he was forced to stop.

The beliefs put forward by Galen were not seriously challenged until the sixteenth century, when Belgian-born Andreas Vesalius published a treatise containing detailed drawings of anatomical parts of human bodies. He was aided by a Paduan judge who supported his work and made bodies of executed criminals available for him to dissect.

Vesalius’s observations disproved Galen’s conclusion that humans and apes shared the same anatomy.

It was around this time that great leaps were being made in knowledge of the structure and function of the circulatory system.

William Harvey, an English physician, was the first to accurately describe how the heart pumped blood around the body.

Abbots Langley-born Thomas Greenhill was a surgeon who wrote an important book about embalming. Surgeon to Henry Howard, Duke of Norfolk, he was (supposedly) born the last of 39 children; 7 sons and 32 daughters.

His book was published in 1705. Its main concern was to stress the importance of embalming for the burial of the aristocracy, and make it a task limited to surgeons.

Doctors and surgeons were hampered by the fact that only certified anatomists were allowed to perform dissections, which were sponsored by city councillors and often charged an admission fee for spectators.

To cope with shortages of cadavers during the seventeenth and eighteenth centuries, body-snatching and even murder were practiced to obtain bodies. Body snatchers would sneak into a graveyard, dig up a corpse and sell it to anatomists for use in dissections. Men who would steal corpses were known as ‘resurrectionists’. The problem was so common that relatives would sometimes guard new graves for a period after burial to prevent their departed loved ones being stolen.

In 1832, Parliament passed the Anatomy Act, which finally provided a legitimate supply of corpses by allowing legal dissection of executed murderers.

During the nineteenth century, anatomical research was extended and women, who were not allowed to attend medical school, could attend anatomy theatres.

French chemist Louis Pasteur discovered germ theory in the 1860s. He discovered that disease came from microorganisms and that bacteria can be killed by heat and disinfectant. This caused doctors to realise the importance of washing their hands and sterilising their instruments.

These early discoveries helped pave the way for recent medical breakthroughs. For example, in 2015 scientists discovered teixobactin, the first new antibiotic in 30 years, and also unveiled a new electron microscope that can provide unprecedented resolution of objects a million times smaller than a human hair.