QI The Book of the Dead

Hunter was the most distinguished anatomist of his day, and it was he who encouraged Jenner to experiment rather than speculate about his scientific ideas. His motto was: ‘Don’t think, try!’ On his two acres of land at Earl’s Court, Hunter kept ostriches, leopards, buffaloes, jackals and snakes, all for his students to carve up and investigate. If need be, he supplemented his supply by bringing in the carcasses of exotic beasts from the Royal Zoo at the Tower of London.
    In 1771, when Joseph Banks returned from James Cook’s first voyage, Hunter recommended Jenner to catalogue his botanical collection. Banks agreed, and was so impressed with Jenner’s work that he invited him to join Cook’s second voyage in 1772. After some hard thought, Jenner decided against it and went back home to set up his own general practice in Gloucestershire. He had also turned down John Hunter’s offer of a partnership, but the two men kept in close touch, with Hunter directing Jenner’s research into natural history by letter. After Jenner suffered a romantic setback, Hunter wrote to him saying:
    Let her go, never mind her. I will employ you with hedge-hogs, for I do not know how far I may trust mine. I want you to get a hedge-hog in the beginning of winter and weigh him; put him in your garden, and let him have some leaves, hay or straw, to cover himself, which he will do; then weigh him in the Spring and see what he has lost .
     
    Jenner was fascinated by hibernation and sceptical ofcontemporary theories that birds (like bats) hibernated in winter. He dissected them and found seeds that came from other countries. He also noted that returning swallows were not, in fact, ‘dirty’ – going against the prevailing wisdom that they spent the winter asleep in the mud at the bottom of ponds.
    His work on bird migration wasn’t published until the very end of his life, but it was an earlier piece of birdlife research that first made his name. In 1787, his ‘Observations on the Cuckoo’ revealed that cuckoo chicks have hollows in their backs, allowing them to scoop up the other baby birds in the nest and tip them over the side. This unique feature is only present for the first twelve days of the cuckoo’s life. Until Jenner’s publication, it had been assumed that it was the foster birds that got rid of their own chicks. His theory wasn’t universally accepted until photography confirmed he was right in the twentieth century, but it was good enough to get him elected to the Royal Society in 1789.
    Close observation was Jenner’s forte and it led to another breakthrough: he was one of the first doctors to make a connection between arteriosclerosis of the coronary arteries and angina. In 1786, he noted that, in one of his patients who had suffered from angina, the coronary arteries were ‘blocked’ with a ‘white fleshy cartilaginous matter’ that made a grating sound when he cut through them. ‘The heart, I believe,’ he wrote, ‘in every subject that has died of the angina pectoris , has been found extremely loaded with fat.’
    Jenner thoroughly enjoyed life in Gloucestershire. He was a popular country-house guest, highly regarded as a witty raconteur, poet and violinist. He was also a natty dresser. According to his friend Edward Gardner, he was usually to be seen in ‘a blue coat, and yellow buttons, buckskin, well polishedjockey boots with silver spurs, and he carried a smart whip with a silver handle’. Like Ben Franklin and Epicurus, he loved like-minded company, and founded two clubs: the Convivio-medical Society and the Medico-convivial Society. They met in separate inns and had, as their names imply, similar interests but opposite priorities. Jenner was also a keen balloonist, a hobby that terrified the local farmers but was to lead him to his future wife, Catherine. His unmanned, varnished-silk balloon landed in the grounds of her father’s estate.
    Edward and Catherine were married in 1788 and had four children. The eldest, Edward, died of tuberculosis aged twenty-one. Jenner was devastated, but, ever the scientist, used the blood from his son’s frequent bleedings to enrich his manure and see if it had any effect on the growth of plants.
    He was forty-seven when he made the discovery that would make him famous. By the late eighteenth century, 60 per cent of the population of Europe was infected with smallpox. A third of those who contracted the disease died and survivors were left horribly