WORLD OF MICROBIOLOGY AND IMMUNOLOGY Historical Chronology647also discovers what becomes known as “Brownian
movement.”1831 Charles Robert Darwin begins his historic voyage on
the H.M.S. Beagle(1831–1836). His observations
during the voyage lead to his theory of evolution by
means of natural selection.1831 Patrick Matthew includes a discussion of evolution
and natural selection in his book On Naval Timber
and Arboriculture. Matthew later claims priority in
the discovery of evolution by means of natural selec-
tion in an article published in 1860 in the journal
Gardeners’ Chronicle.1832 The French physiologist Anselme Payen
(1795–1871) isolates diastase from barley. Diastase
catalyzes the conversion of starch into sugar, and is
an example of the organic catalysts within living tis-
sue that eventually come to be called enzymes.1836 Félix Dujardin describes the “living jell” of the cyto-
plasm, which he calls “sarcode.”1836 Theodor Schwann carries out experiments that refute
the theory of the spontaneous generation of infuso-
ria. He also demonstrates that alcoholic fermentation
depends on the action of living yeast cells. The same
conclusion is reached independently by Charles
Caignard de la Tour.1837 French physiologist René–Joachim Dutrochet
(1776–1847) publishes his research on plant physiol-
ogy that includes pioneering work on osmosis. He is
the first scientist to systematically investigate the
process of osmosis, which he names, and to argue
that chlorophyll is necessary for photosynthesis.1838 Matthias Jakob Schleiden notes that the nucleus first
described by Robert Brown is a characteristic of all
plant cells. Schleiden describes plants as a commu-
nity of cells and cell products. He helps establish cell
theory and stimulates Theodor Schwann’s recogni-
tion that animals are also composed of cells and cell
products.1839 Jan Evangelista Purkinje uses the term “protoplasm”
to describe the substance within living cells.1839 Theodore Schwann extends the theory of cells to
include animals and helps establish the basic unity of
the two great kingdoms of life. He publishes
Microscopical Researches into the Accordance in the
Structure and Growth of Animals and Plants, in
which he asserts that all living things are made up of
cells and that each cell contains certain essential
components. He also coins the term “metabolism” to
describe the overall chemical changes that take place
in living tissues.1840 Friedrich Gustav Jacob Henle publishes the first his-
tology textbook, General Anatomy. This work
includes the first modern discussion of the germ the-
ory of communicable diseases.1840 German chemist Justus von Liebig (1803–1873)
shows that plants synthesize organic compounds
from carbon dioxide in the air but take their nitroge-
nous compounds from the soil. He also states that
ammonia (nitrogen) is needed for plant growth.1840 Karl Bogislaus Reichert introduces the cell theory
into the discipline of embryology. He proves that the
segments observed in fertilized eggs develop into
individual cells, and that organs develop from cells.1842 Charles Robert Darwin writes out an abstract of his
theory of evolution, but he does not plan to have this
theory published until after his death.1842 Theodor Ludwig Wilhelm Bischoff publishes the
first textbook of comparative embryology,
Developmental History of Mammals and Man.1844 Robert Chambers anonymously publishes Vestiges of
the Natural History of Creation,which advocates the
theory of evolution. This controversial book
becomes a best seller and introduces the general
reading public to the theory of evolution.1845 Karl Theodor Ernst von Siebold realizes that proto-
zoa are single-celled organisms. He is the first scien-
tist to define protozoa as organisms.1847 A series of yellow fever epidemics sweeps the
American Southern states. The epidemics recur
every few years for more than 30 years.1851 Hugo von Mohl publishes his Basic Outline of the
Anatomy and Physiology of the Plant Cell, in which
he proposes that new cells are created by cell division.1854 Gregor Mendel begins to study 34 different strains of
peas. He selects 22 kinds for further experiments.
From 1856 to 1863, Mendel grows and tests over
28,000 plants and analyzes seven pairs of traits.1855 Alfred Russell Wallace writes an essay entitled On
the Law Which has Regulated the Introduction of
New Species and sends it to Charles Darwin.
Wallace’s essay and one by Darwin are published in
the 1858 Proceedings of the Linnaean Society.1857 Louis Pasteur demonstrates that lactic acid fermenta-
tion is caused by a living organism. Between 1857
and 1880 he performs a series of experiments that
refute the doctrine of spontaneous generation. He
also introduces vaccines for fowl cholera, anthrax,
and rabies, based on attenuated strains of viruses and
bacteria.•
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