The Microscope
and
Discovery of the Cell
The Microscope
An understanding of cells and the ultrastructure
of cells had to wait until objects so small could
be visualized by magnification.
Origin of the Microscope
• The first record of the
invention of a microscope
was by Hans and
Zacharias Janssen
(Netherlands) in 1590?
• Galileo Galilei improved
the microscope in 1609
(in the same way that he
improved the telescope)
and by 1624-1625
published magnified
drawings of insects.
• Suffered from chromatic
and spherical aberrations
Galileo’s first
microscope from
1609
Illustrations of
honey bees made
with an improved
Galileo microscope
in 1630
Antonie Philips van Leeuwenhoek
Made a powerful single-lens
microscope with which he observed
many types of unicells and tissues. He
even drew bacteria.
A single-lens
microscope
1632-1723,
Netherlands
His drawing
of an ash
stem section
Robert Hooke’s Micrographia
• Hooke (1635-1703, UK) was
intrigued by the reports sent
by van Leeuwenhoek and
built his own microscope on
the design of Galileo
• He confirmed many of the
observations that van
Leeuwenhoek reported
• Made many of his own
original observations
• Published Micrographia in
1665
• Much of the microscopic
work of the rest of the
17th and 18th centuries
was descriptive [and
there was much to
describe].
• Near the beginning of
the 19th century,
microscopes were made
that reduced the
problems of chromatic
aberration
Trunnion Model microscope
made by Charles A. Spencer
(1813-1881), US manufacturer
of microscopes
Ernst Karl Abbe
• Partner of Carl Zeiss
• Optical physicist
• Invented the
apochromatic lens and
corrections to spherical
aberration
• Sought to maximize
resolution of the light
microscope
• Demonstrated the limit
of resolution by visible
light around 0.5μm
1840-1905, Germany
The Cell Theory
…also, by the early part of the 19th century
enough biological material had been observed
to begin to make generalizations.
Matthias Jakob Schleiden
• A botanist and
microscopist
• In 1838 declared that the
plant organism is made of
cells
• He accepted the
importance of the nucleus,
discovered by Robert
Brown (1773-1858), and
speculated on its role in
cell division
1804-1881, Germany
Theodor Schwann
• He was a zoologist and a
microscopist
• Physiologist and
microanatomist
• Discovered the connection
between yeast and
fermentation
• Following Schleiden’s
pronouncement, declared
that animals, too, are made
of cells as the fundamental
building blocks
1810-1882, Germany
Virchow and Remak
• Rudolph Carl Virchow
(1821-1902, Germany)
suggested that disease is
a cellular problem
• He stated that all cells
come from pre-existing
cells, a theory stated
earlier by Robert Remak
(1815-1865, Poland)
Virchow’s cell
theory
Virchow (1821-1902)
Remak (1815-1865)
The Cell Theory by 1858
• All living organisms are composed of one or
more cells.
• The cell is the most basic unit of structure,
function, and organization in all organisms.
• All cells come from pre-existing, living cells.
Histology and Paul Ehrlich
• Aniline dyes had been
derived from coal tars in
the early part of 19th
Century
• Karl Weigert (1845-1904,
Germany) used an aniline
dye to stain bacteria
• Ehrlich experimented with
staining human tissues
• He used chemical
treatments to serve as the
first chemotherapy (used
Methylene Blue for syphilis)
1854-1915, Germany
The use of aniline
dye to stain white
blood cells
Development of Optical Staining
Bright field
Phase-Contrast
Polarized light
Differential Interference
Contrast
Darkfield
Fluorescence Imaging
Walther Flemming
• Used aniline dyes to
visualize nuclei and
chromosomes
• All nuclei come
from other nuclei
• He discovered and
described the
mitotic cell cycle in
cells from the gills
and fins of
salamanders.
1843-1905, Germany
Published in 1882
The Cell Cycle: Mitosis
Reduction Division: Meiosis
• First described by Oskar
Hertwig (1849-1922,
Germany) in 1876 in the
formation of sea urchin
eggs.
• Described again by
Edouard van Beneden
(1846-1910, Belgium) in
1890 in the formation of
Ascaris eggs.
• August Weismann (18341914, Germany) noted in
1911 that the reduction of
chromosome numbers,
employing meiosis, was
necessary if nuclei were to
fuse in sexual reproduction
Meiosis
Electron Microscopy
• Two types: Transmission (TEM) and Scanning (SEM)
Transmission Electron Microscopy
• Leo Szilard (1928) filed patent
for electron microscope in
concept
• The prototype built in 1931 by
Ruska and Knoll
• Resolution limit for light
microscope ~2,000X; but the
limit for TEM ~2 millionX
Max Knoll (1897-1969, Germany, left) and
Ernst Ruska(1906-1988, Germany, right) with
first TEM
Scanning Electron Microscopy
Vladimir Kosmich Zworykin
(1888-1982, Russia and
USA) invented SEM and
television (both based on
raster principle)
With early television
(kinetoscope) in 1929
Details of Subcellular Structures with EM
Membranes
Details of Subcellular Structures with EM
Nucleus
Molecular details of the nuclear
envelope by Mahamid et al. (2016)
A new method for visualizing molecular cellular components using TEM
Details of Subcellular Structures with EM
Chloroplast
Details of Subcellular Structures with EM
Mitochondria
Details of Subcellular Structures with EM
Endoplasmic Reticulum
Details of Subcellular Structures with EM
Flagellum or Cilium
Current View of the Cell Theory
• All known living things are made up of one or more cells.
• All living cells arise from pre-existing cells by division.
• The cell is the fundamental unit of structure and function in
all living organisms.
• The activity of an organism depends on the total activity of
independent cells.
• Energy flow occurs within cells.
• Cells contain hereditary information (DNA) which is passed
from cell to cell during cell division.
• All cells are basically the same in chemical composition in
organisms of similar species.