17
theory of spontaneous generation. Nevertheless, many of his obser-
vations about cells were years ahead of their time.
Other French scientists did important work on cells. In 1809 a
French botany professor named Charles-Francois Brisseau-Mirbel
noted that all plants are made up of cells.That same year French natu-
ralist Jean-Baptiste Lamarck published a book with an entire chapter
devoted to cellular structure in plants. In 1824, years before German
scientists popularized the idea, Henri Dutrochet declared that the
cell is the fundamental unit of organization
in life forms. Dutrochet also named and de-
scribed the process of osmosis. That is how
molecules of fluid—usually water—move
through a cell’s semipermeable membrane
from an area of low concentration to one of
higher concentration. In 1832 French sci-
entist Barthélemy Dumortier described cell
division in plants. Dumortier noticed how a
middle line of partition formed between an
original cell and a new cell, which resulted in
division into two complete cells. Dumortier wrote that this process,
called binary fission, “seems to us to provide a perfectly clear expla-
nation of the origin and development of cells, which has hitherto re-
mained unexplained.”
7
These discoveries would not gain wider accep-
tance in the world until they were affirmed by German scientists in the
following decades.
The Basic Unit of Life
In the 1830s Germany became the center for cell research. This was
largely due to the availability of improvedmicroscopes inGermany. In
1832 Joseph Jackson Lister, an English wine merchant and amateur
in microscopy, invented a spaced system of lenses for microscopes.
This system corrected a problem called chromatic aberration—a dis-
tortion that occurs when wavelengths of colored light are not on the
same focal plane. Lister’s microscope produced sharper images with
greater magnification. It caused scientists to realize that the micro-
scope was no longer a novelty but a reliable tool for research. A decade
later Carl Zeiss started an optical company in Jena, a university town
WORDS IN CONTEXT
semipermeable
Allowing some
materials to pass
through (a membrane)
and holding other
materials out.
