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The History of Cell Theory
B
efore the discovery of cells, there were many theories to account
for the complexities of living things. Some scientists—or nat-
ural philosophers, as they were called in the 1600s—believed that
the bodies of people and animals were composed of different types
of fibers. The varied properties of these fibers explained why tissues
differed from each other in form and function. Other scientists sug-
gested that bodies were made up of some kind of fundamental units,
just as matter is formed from atoms. However, the most popular
theory of how life developed was called spontaneous generation. Ac-
cording to this idea, living things simply sprang up from inanimate
matter. Observations that seemed to support spontaneous genera-
tion were found everywhere in nature. After all, mold grew on food,
maggots appeared on rotting meat, and mushrooms sprouted in the
roots of dead trees. Development of an improved theory about the
makeup of living things required a new invention and a new way to
scrutinize tissue.
The Invention of the Microscope
In their studies of plants and animals, early scientists were limited
by what the naked eye could see and what the imagination could
surmise.This changed around 1590 with the invention of the micro-
scope. Zacharias Jansen and his father, Hans, were Dutch makers
of spectacles and magnifying glasses. In an experiment they aligned
several convex lenses inside a tube and made a key discovery.The de-
vice produced a two-stage magnification. An object near the end of
the tube appeared to be significantly enlarged, magnified much more
than a single lens could accomplish. The Jansens’ compound micro-
scope was somewhat crude, with a blurry image, and it could magnify
CHAPTER ONE
