Deliberate exposure to material from smallpox sores. It aimed to produce a milder illness and carried a lower mortality than naturally acquired smallpox. It was practised in parts of Asia and Africa.

The specific milestone was a successful public demonstration of ether anaesthesia. Morton supplied the agent and Warren operated at Massachusetts General Hospital; the claim is narrower than saying anaesthesia had never been used before.

Blood loss, pain and infection. Anaesthesia addressed pain and enabled longer operations, but safe surgery also required ways to control bleeding and prevent dangerous infections.

Excitation and inhibition. A neurone receives inputs from many synapses, and its response depends on the balance of stimulating and inhibitory effects.

Her autobiography, published in 1857 after the Crimean War. Much of what is known about her life comes from this account; London Museum holds an edition from that year.

Louis Washkansky received the heart of Denise Darvall at Groote Schuur Hospital in Cape Town. Darvall's father agreed to organ donation after the road collision that caused her fatal injuries.

Chemical destruction of infection-causing germs. Lister's system addressed infection during and after operations, helping tackle a major cause of death even when the operation itself had succeeded.