MICROSCOPY: IMAGING OF BIOLOGICAL SPECIMENS - A Guide to Methods in the Biomedical Sciences - page 87

Chapter 5

MICROSCOPY: IMAGING OF
BIOLOGICAL SPECIMENS

A. Introduction

Imaging technologies seek to peer inside tissues, cells, or even an en-
tire organism, including man, to reveal underlying structures. The most
common methods of imaging use the microscope. The use of micro-
scopes has become an essential part of almost every field of biomedical
sciences, and is particularly important in the field of Cell Biology, which
seeks to understand how cells are organized and function.
Anton van Leeuwenhoek of Holland is generally considered to be
the father of the microscope. The first “light microscope” was invented
by him in the mid century. Convex lenses, the essential compo-
nent required for magnification, had been developed about 100 years
earlier. The single lens design limited the amount of magnification pos-
sible. The development of the compound microscope late in the
century helped overcome this limitation. A compound microscope is a
microscope consisting of 2 lenses, one the “objective” and the second
the “eyepiece”. It was with these early microscopes that the Englishman
Robert Hooke looked at the unseen world and gave the name “cell” to de-
scribe the smallest observable structures that made up living organisms.
Later, Louis Pasteur was able to identify yeast organisms, and Robert
Koch discovered the bacilli (rod shaped bacteria) that cause tubercu-
losis (Mycobacterium tuberculosis) and cholera (Vibrio cholerae).
Real changes in microscope design did not occur until the century
when Carl Zeiss, the founder of the microscope company, began to stan-
dardize compound microscope design and engaged experts in optics to
improve the quality of the lenses used in microscopes. These designs
helped push the light microscope to the limits of its capabilities.
The development of the electron microscope by Max Knoll and Ernst
Ruska in Germany in the early 1930's was the first truly significant