Julius Axelrod (1912-2004), US biochemist, with a laboratory rat. He is taking blood samples from the tail of the rat during a study into the way the drug hexobarbitol is metabolised. Axelrod won the 1970 Nobel Prize for Physiology or Medicine for his work on neurotransmitters, the chemical messengers that link nerve cells in the brain. He was born in New York in 1912, and spent much of his early adulthood working as a food technician. In 1955 he dropped out to take a PhD, and went on to become chief of pharmacology at the National Institute of Mental Health. His discoveries about brain chemistry helped to shed light on the causes of mental illnesses like Parkinson's disease. Photographed on 11 October 1954.