Who is John Bennett from The Emperor of All Maladies: A Biography of Cancer and what is their importance?

In 1845, John Bennett, a Scottish physician, had described the case of a 28-year-old slate layer who complained of a mysterious swelling in his spleen. After much investigation Bennett discovered that the patient's blood had an extremely high level of white blood cells - the principal constituents of pus. While the presence of the pus explained the swelling in the man's spleen, it could not explain the nature of the pus.