156 • The Abyss- He suggested that Oldenburg have it reprinted in London to help doc-
tors treating plague. To the end of his days, Boyle continued probing into the
natural causes of epidemic diseases.^48
Thomas Willis came closer to a breakthrough on plague, perhaps because
of his medical experience.^49 William Harvey’s demonstration of the rapid
circulation of the blood had helped to turn him against bloodletting except
in certain treatments (e.g., cutting off an artery supplying a tumor, thereby
depriving it of life-nourishing blood). Willis believed that the body at-
tempted to cure itself through fermentation of the blood, and in his work on
fevers he had speculated that this was the body’s way of expelling pestilential
poison. But at a crucial point in proclaiming his new vision of fermentation,
Willis returned to a traditionalist view that the body humors should be kept
at an “equal temper and motion of fermentation.” This strictly Galenic inter-
pretation flew in the face of his previous work. Perhaps he felt constrained by
his acceptance into the College of Physicians in 1666.^50
The microscope was just coming into use, promising unprecedented dis-
coveries in medical science. A generation before, Galileo’s telescope had
opened up a new world of sunspots and revealed the moons of Jupiter. Ex-
perimental scientists on the Continent and in Britain reported seeing “an-
imacules” in the human body through their crude microscopes, following up
on Fracastoro’s theory of the seedlets of disease. “The seeds of most [an-
imacules] are so small,” one observer said, “that 190 , 000 of them laid to-
gether in a straight line, did not exceed the length of a barley corn.”^51
By chance, two studies on the uses of the microscope appeared in Lon-
don’s bookshops as plague was advancing into the suburb of Saint Giles in
the Fields. The ever-enthusiastic Pepys was captivated by Hooke’s treatise,
which he picked up in Saint Paul’s churchyard. He missed a timelier message
in the companion volume by Hooke’s friend Marchamont Nedham. Spurred
on by Fracastoro, Nedham had looked for visual evidence of “certain Atoms,
Corpuscles or Particles, sometimes animated into little invisible worms as in
the case of Pestilential infection.” Athanasius Kircher had seen these crea-
tures through his microscope, Nedham said, and had postulated: “Upon the
opening of buboes and tumors, they have been found full of innumerable
vermicules indiscernible by the eye.”^52
Only one person at this time had a microscope powerful enough to detect
the small “atoms” that Kircher discussed. Using a self-made microscope with
a magnification of 400 x,the Dutch draper Anton van Leeuwenhoek saw hu-
man sperm and “animacules” that resembled the long-sought-after “seeds” of
plague. He wrote the Royal Society about his findings, but the English vir-