14
their toy kaleidoscopes up to the sky. No prior microscopist, not even
the great Robert Hooke, had ever thought simply to look at a droplet
of water lighted from behind.”
4
In the 1670s Leeuwenhoek set about studying every substance he
could think to peer at through the eyepiece.This included the plaque
scraped from his own teeth. As Leeuwenhoek described it in a letter
to the Royal Society, a renowned group of scientists in London, “I
then most always saw, with great wonder, that in the said matter there
were many very little living animalcules, very prettily a-moving. The
biggest sort . . . had a very strong and swift motion, and shot through
the water (or spittle) like a pike does through the water.”
5
What Leeu-
wenhoek called animalcules, or little animals, were single-celled bac-
teria. He also observed blood cells, sperm cells, and intestinal proto-
zoa. Unlike Hooke, Leeuwenhoek seemed to perceive that cells were
not merely empty compartments. His description of globules within
blood cells probably referred to cell nuclei. Although no artist him-
self, he also oversaw precise illustrations of his many findings.
Isolated in his hometown of Delft, Hol-
land, and lacking formal education, Leeu-
wenhoek tried to reach out to other scien-
tists for advice. A Dutch diplomat wrote to
Hooke onLeeuwenhoek’s behalf, butHooke
never replied. Over the years, however, the
former cloth merchant gained fame for his
work. In 1680 Leeuwenhoek was named a
full member of the Royal Society, although
he never traveled to England for a single meeting. He continued to
use the microscope to examine everything from crystals to fossils, and
was the first person to see all sorts of microscopic animals. Leeuwen-
hoek, the unlikely scientist, made discoveries related to cell theory
that would be unsurpassed for 150 years.
Preparing the Way for Cell Theory
Before cell theory took shape, scientists continued to learn more
about cells. In France biologist and chemist Francois-Vincent Ra-
spail made important discoveries about the structure and function
WORDS IN CONTEXT
protozoa
Tiny one-celled
animals that are
parasites.
