1. The Microscope and Cell Theory

2. The Microscope
An understanding of cells and the ultrastructure of cells had to wait until objects so small could be visualized by magnification.

3. 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 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

4. 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
, Netherlands
His drawing of an ash stem section

5. Robert Hooke’s Micrographia
Hooke ( , 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

6. 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 ( ), US manufacturer of microscopes

7. 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
, Germany

8. The Cell Theory
…also, by the early part of the 19th century enough biological material had been observed to begin to make generalizations.

9. 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 ( ), and speculated on its role in cell division
, Germany

10. 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
, Germany

11. Virchow and Remak
Virchow’s cell theory
Rudolph Carl Virchow ( , 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 ( , Poland)
Virchow ( )
Remak ( )

12. 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.

13. Histology and Paul Ehrlich
Aniline dyes had been derived from coal tars in the early part of 19th Century
Karl Weigert ( , 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)
, Germany
The use of aniline dye to stain white blood cells

14. Development of Optical Staining
Bright field
Polarized light
Darkfield
Phase-Contrast
Differential Interference
Contrast
Fluorescence Imaging

15. Electron Microscopy
Two types: Transmission (TEM) and Scanning (SEM)

16. 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 ( , Germany, left) and Ernst Ruska( , Germany, right) with first TEM

17. Scanning Electron Microscopy
Vladimir Kosmich Zworykin ( , Russia and USA) invented SEM and television (both based on raster principle)
With early television (kinetoscope) in 1929

18. 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.