Theodor Wilhelm Engelmann
Encyclopedia
Theodor Wilhelm Engelmann (1843 in Leipzig
– 1909) was a German
botanist, physiologist, microbiologist
, university
professor
, and musician whose 1882 experiment measured the effects of different colors of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast
.
and medicine
first at the University of Jena, from 1861 to 1862, and later at the University of Heidelberg, the University of Göttingen and the University of Leipzig
. In 1867, he received a doctoral degree in medicine at Leipzig.
He later taught physiology at the University of Utrecht, becoming a professor in 1888. In 1897, he began teaching physiology at the University of Berlin, where he also became the editor of the Archiv für Anatomie und Physiologie. He retired in 1908, but continued to serve as editor until his death.
s. Focusing on the visible bands of fibers in the muscles, he noted that the volume of the anistropic band increased during contraction, whereas the volume of the isotropic band
decreased. He theorized
that it was this interaction between the two bands which allowed for muscle contraction
.
He also demonstrated, after experiment
s with dissected frog
s in 1875, that contractions of the heart
were caused by the heart muscle itself, not an external nerve
stimulus, as was previously believed.
Engelmann performed three significant experiments involving photosynthesis:
In 1881, he observed the movement of bacteria towards the chloroplasts in a strand of “Spirogyra
” algae. Engelmann hypothesized that the bacteria were moving in response to oxygen generated by the photosynthetically active chloroplasts in the algae. This was one of the first documented observations of positive aerotaxis in bacteria. In 1882, he performed his famous action spectrum experiment using a device designed and built by Carl Zeiss
. The modified microscope had a prism which could produce a microscopic spectrum on a microscope slide. The device could also distinguish and measure different wavelengths of light making it a “micro-spectroscope.” Engelmann used this device to illuminate a strand of Cladophora
(not Spirogyra) with light from the visible spectrum
, exposing different sections to different wavelengths (or colors of light). He added the oxygen seeking bacteria B. termo to this setup and noted where they accumulated (Note: Four years later, Hauser concluded that B. termo had been mislabeled and was not one, but three species of bacteria of the genus Proteus ). Their clumping allowed him to see which regions had the highest concentration of oxygen. He concluded that the most photosynthetically active regions will have the highest concentrations of bacteria. The bacteria accumulated in the regions of red and blue light, showing that these wavelengths of light generated the most photosynthetic activity. However, his experiment was somewhat flawed because he used the sun as his lightsource. He failed to account for the fact that the sun does not emit all visible wavelengths of light at the same intensity. However, further analysis of plant pigments proved that his results were valid. A year later Engelmann discovered that purple bacteria
utilise ultraviolet
light in the same way.
dedicated his String Quartet No. 3
to Engelmann, an amateur cellist who had hosted him on a visit to Utrecht.
Leipzig
Leipzig Leipzig has always been a trade city, situated during the time of the Holy Roman Empire at the intersection of the Via Regia and Via Imperii, two important trade routes. At one time, Leipzig was one of the major European centres of learning and culture in fields such as music and publishing...
– 1909) was a German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
botanist, physiologist, microbiologist
Microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...
, university
University
A university is an institution of higher education and research, which grants academic degrees in a variety of subjects. A university is an organisation that provides both undergraduate education and postgraduate education...
professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
, and musician whose 1882 experiment measured the effects of different colors of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
.
Academic history
Englemann studied natural scienceNatural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...
and medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
first at the University of Jena, from 1861 to 1862, and later at the University of Heidelberg, the University of Göttingen and the University of Leipzig
University of Leipzig
The University of Leipzig , located in Leipzig in the Free State of Saxony, Germany, is one of the oldest universities in the world and the second-oldest university in Germany...
. In 1867, he received a doctoral degree in medicine at Leipzig.
He later taught physiology at the University of Utrecht, becoming a professor in 1888. In 1897, he began teaching physiology at the University of Berlin, where he also became the editor of the Archiv für Anatomie und Physiologie. He retired in 1908, but continued to serve as editor until his death.
Scientific investigations
Engleman's major contribution to the field of physiology emerged from a study lasting from 1873 to 1897, in which he observed the contractions of striated muscleStriated muscle
Striated muscle tissue is a form of fibers that are combined into parallel fibers. More specifically, it can refer to:* Cardiac muscle .* Skeletal muscle* Branchiomeric muscles...
s. Focusing on the visible bands of fibers in the muscles, he noted that the volume of the anistropic band increased during contraction, whereas the volume of the isotropic band
Isotropic bands
In physiology, isotropic bands are skeletal muscle cells that form the light bands that contribute to the striated pattern of the cells.Isotropic bands indicate the behavior of polarized light as it passes through I bands....
decreased. He theorized
Theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
that it was this interaction between the two bands which allowed for muscle contraction
Muscle contraction
Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...
.
He also demonstrated, after experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...
s with dissected frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s in 1875, that contractions of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
were caused by the heart muscle itself, not an external nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
stimulus, as was previously believed.
Engelmann performed three significant experiments involving photosynthesis:
In 1881, he observed the movement of bacteria towards the chloroplasts in a strand of “Spirogyra
Spirogyra
Spirogyra is a genus of filamentous green algae of the order Zygnematales, named for the helical or spiral arrangement of the chloroplasts that is diagnostic of the genus. It is commonly found in freshwater areas, and there are more than 400 species of Spirogyra in the world. Spirogyra measures...
” algae. Engelmann hypothesized that the bacteria were moving in response to oxygen generated by the photosynthetically active chloroplasts in the algae. This was one of the first documented observations of positive aerotaxis in bacteria. In 1882, he performed his famous action spectrum experiment using a device designed and built by Carl Zeiss
Carl Zeiss
Carl Zeiss was a German maker of optical instruments commonly known for the company he founded, Carl Zeiss Jena . Zeiss made contributions to lens manufacturing that have aided the modern production of lenses...
. The modified microscope had a prism which could produce a microscopic spectrum on a microscope slide. The device could also distinguish and measure different wavelengths of light making it a “micro-spectroscope.” Engelmann used this device to illuminate a strand of Cladophora
Cladophora
Cladophora is a genus of reticulated filamentous Ulvophyceae . The genus Cladophora contains many species that are very hard to tell apart and classify, mainly because of the great variation in their appearances, which is affected by habitat, age and environmental conditions...
(not Spirogyra) with light from the visible spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
, exposing different sections to different wavelengths (or colors of light). He added the oxygen seeking bacteria B. termo to this setup and noted where they accumulated (Note: Four years later, Hauser concluded that B. termo had been mislabeled and was not one, but three species of bacteria of the genus Proteus ). Their clumping allowed him to see which regions had the highest concentration of oxygen. He concluded that the most photosynthetically active regions will have the highest concentrations of bacteria. The bacteria accumulated in the regions of red and blue light, showing that these wavelengths of light generated the most photosynthetic activity. However, his experiment was somewhat flawed because he used the sun as his lightsource. He failed to account for the fact that the sun does not emit all visible wavelengths of light at the same intensity. However, further analysis of plant pigments proved that his results were valid. A year later Engelmann discovered that purple bacteria
Purple bacteria
Purple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, that is capable of producing energy through photosynthesis...
utilise ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light in the same way.
Musical significance
Johannes BrahmsJohannes Brahms
Johannes Brahms was a German composer and pianist, and one of the leading musicians of the Romantic period. Born in Hamburg, Brahms spent much of his professional life in Vienna, Austria, where he was a leader of the musical scene...
dedicated his String Quartet No. 3
String Quartet No. 3 (Brahms)
The String Quartet No. 3 in B flat major, Op. 67, was composed by Johannes Brahms in the summer of 1875 and published by the firm of Fritz Simrock. It received its premiere performance on October 30, 1876 in Berlin. The work is scored for two violins, viola, and cello, and has four movements:* I....
to Engelmann, an amateur cellist who had hosted him on a visit to Utrecht.
External links
- Short biography, bibliography, and links on digitized sources in the Virtual LaboratoryVirtual LaboratoryThe online project Virtual Laboratory. Essays and Resources on the Experimentalization of Life, 1830-1930, located at the Max Planck Institute for the History of Science, is dedicated to research in the history of the experimentalization of life...
of the Max Planck Institute for the History of ScienceMax Planck Institute for the History of ScienceThe Max Planck Institute for the History of Science in Berlin was established in March 1994. Its research is primarily devoted to a theoretically oriented history of science, principally of the natural sciences, but with methodological perspectives drawn from the cognitive sciences and from... - Original Source for Action Spectrum Experiment
- Bacterial Method
- Pictoral Demonstrations of Photosynthesis
- Timeline of Photosyntheis
- Contributions of Theodor Wilhelm Engelmann on phototaxis, chemotaxis and photosynthesis
- B. termo Information