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Chapter 7

BIOL 3200 Chapter Notes - Chapter 7: Protozoology, Naturphilosophie, Middle Ear


Department
Biology
Course Code
BIOL 3200
Professor
Jan Sapp
Chapter
7

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Biol 3200
Chapter 7: The Myth of the Cell Theory
Biologists of the second half of the 19th century often claimed that the cell held the key
to all biological problems
o All distinctive vital processes such as metabolism, growth, reproduction, sexual
phenomena and heredity could be reduced to the activities in cells
Cell theory was comprised of 3 tenets:
o All plants and animals are made of cells
o All cells arise from division of pre-existing cells
o All cells possess the attributes of life (assimilation, growth, and reproduction)
No other biological theory (other than evolutionary theory) brought so many diverse
phenomena under one point of view or did more for the unification of biological
knowledge
In medical research, cell theory created a new era in physiology and pathology
o Based on the idea that all functions of the body in health and disease were
outward expressions of cell activities
In evolutionary biology, cell theory underscored the unity of life
Every organism is, or at some time has been, a cell
An Historical Paradox
Cell theory was founded by Matthias Jacob Schleiden and Theodor Schwann
American cytologist Edmund Beecher Wilson said that the cell theory developed by
“hleide ad “ha as oe of the oadig ladarks of the 1th etury
Historians also credited them as founders of cell theory
Some biologists said that what has been attributed to them has been discovered by
others and what they thought they had discovered contradicted fundamental principles
of the cell theory
Schleiden and Schwann maintained the first tenet that all organisms are made up of
cells → this idea did ot origiate ith the
Predecessors of the idea:
o In 1808 and 1809, Brisseau de Mirbel (professor of botany at the Musée
d’Histoire Naturelle i Paris) recognized the presence of cells in plants
o Lamarck wrote an entire chapter in Philosophie Zoologique about cellular tissues
o They knew that organisms were made of cells but none of them knew that the
cell is an independent unit of life (second tenet)
Schleiden was the first to propose the second principle that the cell possesses all
characteristics of life and that plants and animals are made up of cells
Henri Dutrochet wrote in 1824 that the cell is the fundamental unit of organization
In 1826, J.P.F Turpin wrote in a memoir that not only are plants composed of cells but
the cells are distinct individualities that form the composite individuality of plants
Schleiden believed that cells did not arise by division but by reproduction of new cells
inside mother cells by a slimy substance that first made the nucleus and then the cell
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In 1833, Scottish botanist Robert Brown said that this round body, which he named the
areola or nucleus was a general feature of several plant cells
Schleiden renamed the nucleus cytoblast and said that it was formed by accumulation of
granulated mucus and that afterwards it creates the cell
Schwann adopted this model and applied it to animal cells; he named the cell-
generating slime cytoblastem
Schwann said that the process of crystallization in inorganic nature is analogous to the
formation of cells
Cells from Cells
Free cell formation: cells arose from undifferentiated chemical substances called
cytoblastem
o This conflicted with the theory that new cells arose by division of existing cells
In 1832, Cuvier presented Barthélemy Charles Dumortier’s paper to the Académie des
Sciences in which he had talked about cell division
German botanist Hugo Mohl reported cell division in a paper in 1837
Mohl and Austrian Franz Unger did not agree with “hleides theory
Some biologists like Carl von Nägeli adopted an intermediate view that some cells arose
y diisio ad soe arose y “hleide’s ethod
Free ell foratio as ritiized ostly y those ho studied ith “ha’s entor,
Johannes Müller
Müller was well known for his studies in comparative anatomy and physiology
o He studied the passage of nerve impulses from the brain and spinal cord, thus
elucidating the concept of reflex action
o He traced the development of genitalia, discovering the llerian duct which
forms the female internal sexual organs
o He contributed to the knowledge of the composition of blood, the process of
coagulation, formation of images on the retina of the eye, and propagation of
sound in the middle ear
o He also concentrated on the cellular structure of tumors
Müller’s On the Nature and Structural Characteristics of Cancer, and of Those Morbid
Growths Which May Be Confounded with It (1838) established pathological histology
Robert Remak and Rudof Virchow ere Müller’s studets ho eae leaders of ell
research and established the theory that cells arise only from cells
Remak considered the theory of free cell formation to be as unlikely as the spontaneous
generation of organisms
By 1852, Remak has been studying problems of cell generation for a decade
He was unable to get a salaried university position so he focused on clinical practice
where he specialized in neurology and introduced the use of electric therapy for
nervous disorders
Virchow acquired a reputation from his writings on pathology and from his journal
Archive fïr Pathologische Anatomie und Physiologie which he founded in 1847
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