Schleiden and Schwann are the first masons of the cell theory. Schleiden and Schwann: cell theory

The appearance in the scientific community in the middle of the 19th century of the cell theory, the authors of which were Schleiden and Schwann, became a real revolution in the development of all areas of biology without exception.

Another creator of cell theory, R. Virchow, is known for this aphorism: “Schwann stood on the shoulders of Schleiden.” The great Russian physiologist Ivan Pavlov, whose name is known to everyone, compared science to a construction site, where everything is interconnected and everything has its own preceding events. The “construction” of the cell theory is shared with the official authors by all predecessor scientists. On whose shoulders did they stand?

Start

The creation of the cell theory began about 350 years ago. The famous English scientist Robert Hooke invented a device in 1665, which he called a microscope. The toy interested him so much that he looked at everything that came to hand. The result of his passion was the book “Micrography”. Hooke wrote it, after which he began to enthusiastically engage in completely different research, and completely forgot about his microscope.

But it was the entry in his book No. 18 (he described the cells of an ordinary cork and called them cells) that glorified him as a discoverer cellular structure all living things.

Robert Hooke abandoned his passion for the microscope, but it was picked up by world-famous scientists - Marcello Malpighi, Antonie van Leeuwenhoek, Caspar Friedrich Wolf, Jan Evangelista Purkinje, Robert Brown and others.

An improved microscope model allows the Frenchman Charles-François Brissot de Mirbel to conclude that all plants are formed from specialized cells united in tissues. And Jean Baptiste Lamarck transfers the idea of ​​​​tissue structure to organisms of animal origin.

Matthias Schleiden

Matthias Jakob Schleiden (1804-1881), at the age of twenty-six, delighted his family by giving up his promising law practice and going to study at the medical faculty of the same Gettin University, where he received his education as a lawyer.

He did this for good reason - at the age of 35, Matthias Schleiden became a professor at the University of Jena, studying botany and plant physiology. Its goal is to find out how new cells are formed. In his works, he correctly identified the primacy of the nucleus in the formation of new cells, but was mistaken about the mechanisms of the process and the lack of similarity between plant and animal cells.

After five years of work, he writes an article entitled “On the Question of Plants,” proving the cellular structure of all parts of plants. The reviewer of the article, by the way, was the physiologist Johann Muller, whose assistant at that time was the future author of the cell theory T. Schwann.

Theodor Schwann

Schwann (1810-1882) dreamed of becoming a priest since childhood. He went to the University of Bonn to study as a philosopher, choosing this specialization as closer to his future career as a clergyman.

But youthful interest in natural sciences won out. Theodor Schwann graduated from the university at the Faculty of Medicine. For only five years he worked as an assistant to the physiologist I. Muller, but over these years he made so many discoveries that would be enough for several scientists. Suffice it to say that he discovered pepsin in gastric juice, and a specific fiber sheath in nerve endings. The novice researcher rediscovered yeast fungi and proved their involvement in fermentation processes.

Friends and associates

The scientific world of Germany at that time could not help but introduce future comrades. Both recalled meeting over lunch in a small restaurant in 1838. Schleiden and Schwann casually discussed current affairs. Schleiden talked about the presence of nuclei in plant cells and his way of viewing the cells using microscopic equipment.

This message turned the lives of both of them upside down - Schleiden and Schwann became friends and communicated a lot. After only a year of persistent study of animal cells, the work “Microscopic Studies on the Correspondence in the Structure and Growth of Animals and Plants” (1839) appeared. Theodor Schwann was able to see the similarities in the structure and development of elementary units of animal and plant origin. And the main conclusion is that life is in a cage!

It was this postulate that entered biology as the cell theory of Schleiden and Schwann.

Revolution in biology

Like the foundation of the building, the discovery of the cell theory of Schleiden and Schwann launched a chain reaction of discoveries. Histology, cytology, pathological anatomy, physiology, biochemistry, embryology, evolutionary studies - all sciences began to actively develop, discovering new mechanisms of interaction in a living system. The German, like Schleiden and Schwann, the founder of pathanatomy Rudolf Virchow in 1858 supplemented the theory with the proposition “Every cell is a cell” (in Latin - Omnis cellula e cellula).

And the Russian I. Chistyakov (1874) and the Pole E. Strazburger (1875) discovered mitotic (vegetative, not sexual) cell division.

From all these discoveries, like bricks, the cellular theory of Schwann and Schleiden is built, the main postulates of which remain unchanged today.

Modern cell theory

Although in the one hundred and eighty years since Schleiden and Schwann formulated their postulates, experimental and theoretical knowledge has been obtained that has significantly expanded the boundaries of knowledge about the cell, the main provisions of the theory are almost the same and are briefly as follows:

• The unit of all living things is the cell - self-renewing, self-regulating and self-reproducing (the thesis of the unity of origin of all living organisms).
• All organisms on the planet have a similar cell structure, chemical composition and life processes (the thesis of homology, the unity of origin of all life on the planet).
• A cell is a system of biopolymers capable of reproducing what is like from what is not like itself (the thesis of the main property of life as a determining factor).
• Self-reproduction of cells is carried out by dividing the mother (thesis of heredity and continuity).
• Multicellular organisms are formed from specialized cells that form tissues, organs, and systems that are in close interconnection and mutual regulation (the thesis of an organism as a system with close intercellular, humoral, and nervous relationships).
• Cells are morphologically and functionally diverse and acquire specialization in multicellular organisms as a result of differentiation (the thesis of totipotency, the genetic equivalence of cells of a multicellular system).

End of "construction"

Years passed, an electron microscope appeared in the arsenal of biologists, researchers studied in detail the mitosis and meiosis of cells, the structure and role of organelles, cell biochemistry, and even deciphered the DNA molecule. German scientists Schleiden and Schwann, together with their theory, became the support and foundation for subsequent discoveries. But we can definitely say that the system of knowledge about the cell is not yet complete. And every new discovery, brick by brick, advances humanity towards understanding the organization of all life on our planet.

(1804-1881) German biologist

Matthias Jacob Schleiden was born on April 5, 1804 in Hamburg. After graduating from high school in his hometown, in 1824 he entered the law faculty of the University of Heidelberg, intending to devote himself to lawyering. However, he did not achieve success in the legal field. At the age of 27, fascinated by natural history, he abandoned law, thoroughly studied medicine and botany, and soon became a professor of botany at the University of Jena.

Schleiden took up a very interesting problem - the cellular nature of plants. In the two hundred years since Hooke's discovery, a lot of data on the cellular structure of plants has accumulated. In 1671, the Italian biologist Malpighi discovered that “sacs,” as he called cells, were found in various plant organs. Such outstanding scientists as Johann Muller, Purkinje and others worked on the problems of the cellular structure of plants and animals. And yet none of them could speak out in favor of the cellular structure of living matter. This was done almost simultaneously by two scientists. One of them was Matthias Jakob Schleiden.

Having learned about R. Brown's discovery of nuclei in plant cells, Schleiden put forward a theory about the origin of cell tissues. From his point of view, nuclei appear at the very first stage of development of a living cell. Cell vesicles then begin to grow around the nuclei until they collide with each other. He expressed this profound thought very convincingly. To prove his theory, Schleiden began laboratory research. He began to methodically look through section after section, looking for nuclei, then shells, repeating his observations over and over again on sections of organs and parts of plants. Which plants should be taken for analysis - adult, fully formed plants or young, still underdeveloped plants? It’s probably wiser to take ones that are already ripe. This is what most scientists did. But this was the mistake: scientists forgot the main thing - the history of the development of organs and tissues. Schleiden from the very beginning chose a different path: he decided to follow how the plant gradually develops, how young, not yet differentiated cells grow, change their shape and finally become the basis of a mature plant.

After five years of methodical research, he proved that all plant organs are cellular in nature. Having completed his work, Schleiden submitted it for publication to the journal “Müller Archive,” which was edited by the German botanist I. Müller. The article was called “On the question of plant development.”

In the section on the origin of plants, he presented his theory of the emergence of progeny cells from the mother cell. Schleiden's work was the impetus for Theodor Schwann to undertake lengthy and careful microscopic studies, which proved the unity of the cellular structure of everything organic world.

At the end of his life, the German scientist left his beloved botany and took up anthropology - the science of differences in appearance, structure and activity of the organism of individual human groups in time and space. He receives the title of professor of anthropology at the University of Dorpat. Schleiden died on June 23, 1881 in Frankfurt am Main.

(April 5, 1804, Hamburg - June 23, 1881, Frankfurt am Main) - German biologist. Main directions scientific research- cytology and embryology of plants. His scientific achievements contributed to the creation of cell theory.

In 1827 he graduated from the University of Heidelberg. In 1839-1862. - Professor of botany (University of Jena), since 1850 he became director of the botanical garden at this university. In 1863-1864. - Professor of Anthropology (University of Dorpat).

In 1842-1843. In his work “Fundamentals of Scientific Botany,” Schleiden, using the inductive method, criticized the natural philosophical and narrowly systematic aspects in the works of his contemporaries. Considered a reformer of botany.

Schleiden's main works are on embryology and plant anatomy. Schleiden used and substantiated the ontogenetic method of studying plant morphology and was its active promoter.

Schleiden's work played an important role in the creation of cell theory. Schleiden was considered one of the predecessors and supporters of Darwinism.

Schleiden's research contributed to the creation of T. Schwann's cell theory. Schleiden's works on the development and differentiation of cellular structures of higher plants are known. In 1842 he first discovered nucleoli in the nucleus.

According to modern ideas, Schleiden's specific studies contained a number of errors: in particular, Schleiden believed that cells could arise from structureless matter, and the plant embryo could develop from a pollen tube.

In his hometown, he graduated from high school, and in 1824 he entered the law faculty of Heidelberg University, intending to devote himself to lawyering. Despite the fact that he graduated with honors, he did not become a lawyer.

Schleiden then studied philosophy and medicine at the University of Göttingen. He eventually became interested in biological sciences, devoting himself to physiology and botany. He published his first work on plants at the age of 33.

In 1837 Schleiden proposed new theory formation of plant cells, based on the idea of ​​the decisive role of the cell nucleus in this process. He believed that the new cell was, as it were, blown out of the nucleus and then covered with a cell wall. Despite its fallacy, this theory had a positive meaning, because attracted the attention of researchers to the study of the structure of the cell and nucleus.

It was then that, together with zoologist Theodor Schwann, Schleiden began microscopic research, which led scientists to develop the cellular theory of the structure of organisms.

In 1839, Schleiden received his Ph.D. from the University of Jena.

He received his doctorate in medicine in 1843 at the University of Tübingen, and from 1863 he was a professor of phytochemistry (the science of chemical processes in living plants) and anthropology in Dorpat, and also led scientific work in Dresden, Wiesbaden and Frankfurt.

From 1840 to 1862 he was a professor of botany in Jena, in 1863 he was invited to read anthropology and plant chemistry in Dorpat, but already in 1864 he abandoned this position and lived mostly in Dresden and Wiesbaden. Brilliantly and versatilely educated, with an excellent command of the pen, merciless in criticism and polemics, the Kantian Schleiden rebelled against the then dominant trends in botany, the narrow systematic nomenclature and speculative, natural philosophy. He called representatives of the 1st direction “hay gatherers” and no less criticized the unfounded fantasies of natural philosophers. Schleiden demands that botany should stand at the same height as physics and chemistry, its method should be inductive, and it should have nothing in common with natural philosophical speculations; the basis of plant morphology should be the study of the history of the development of forms and organs, their genesis and metamorphoses, and not a simple listing of the organs of phantom plants; The natural plant system will be correctly understood only when not only higher plants are studied, but also, mainly, lower ones (algae and fungi). Both of these ideas of Schleiden quickly spread among botanists and brought the most beneficial results. Schleiden is one of the most important botanical reformers and founders of new (scientific) botany. In his works, he brilliantly refuted the old direction and presented so many problems for botany that they could be solved not by one person, but by a whole generation of observers and thinkers. Schleiden's abilities as a writer contributed to the success of his popular works, some of which went through several editions and were translated into Russian: “Die Pflanze und Ihr Leben” (1st ed., Leipzig, 1847; Russian translation “The Plant and Its Life”) ; “Studien” (Russian translation of “Etudes”, 1860); “Das meer” (Russian translation of “The Sea”, 1867); “Für Baum und Wald” (1870, Russian translation “Tree and Forest”); "Die Rose" (1873); "Das Salz" (1875), etc.

Being a progressive scientist, Schleiden took an active part in public life. He published many popular science works. Schleiden's works on the development and differentiation of cellular structures of higher plants are known. In 1842 he first discovered nucleoli in the nucleus. Among the most famous works of the scientist is the book “Fundamentals of Botany” (“Grundzge der Botanik”, 1842-1843), which marked the emergence of modern scientific botany. It was Schleiden, thanks to his discoveries in the field of plant physiology, who initiated a debate between biologists that lasted over 20 years.
Scientists did not want to admit the validity of Schleiden's views. As an argument against the facts he presented, the reproach was put forward that his previous works on botany contained errors and did not provide convincing evidence of theoretical generalizations. Schleiden published a number of works on the physiology and anatomy of plants. In the book “Data on Phytogenesis”, in the section on the origin of plants, Schleiden presented his theory of the emergence of progeny cells from the mother cell. Schleiden's work prompted Theodor Schwann to undertake lengthy and careful microscopic studies that proved the unity of the cellular structure of the entire organic world. The scientist’s work entitled “The Plant and Its Life” was published in 1850 in Leipzig.

Main work Schleiden's "Fundamentals of Scientific Botany in two volumes" was published in 1842-1843 in Leipzig and had a huge influence on the reform of plant morphology based on ontogeny. Ontogenesis distinguishes three periods in the development of an individual organism:
formation of germ cells, i.e. pre-embryonic period, limited to the formation of eggs and sperm;
embryonic period - from the beginning of egg division to the birth of the individual;
postpartum period - from the birth of an individual until his death.
At the end of his life, Schleiden left botany and took up anthropology, i.e. the science of differences in the appearance, structure and activity of organisms of individual human groups in time and space.

M. Schleiden studied the emergence of cells during growth various parts plants, and this problem was self-sufficient for him.

As for the cell theory itself in the sense as we understand it at the present time, he did not study it. Schleiden's main merit is his clear formulation of the question regarding the origin of cells in the body. This problem acquired fundamental importance, since it pushed researchers towards studying cellular structure from the point of view of developmental processes. The most significant is Schleiden's idea of ​​the nature of the cell, which he apparently first called an organism. So he wrote: “It is not difficult to understand that both for the physiology of plants and for general physiology, the vital activity of individual cells is the most important and completely inevitable basis, and therefore, first of all, the question arises of how this small, peculiar organism, the cell, actually arises.”

Schleiden's theory of cell formation was later called by him the theory of cytogenesis. It is very significant that she was the first to connect the question of the origin of a cell with its contents and (primarily) with the nucleus; Thus, the attention of researchers was transferred from the cell membrane to these incomparably more important structures.

Schleiden himself believed that he was the first to raise the question of the emergence of “letlets,” although botanists before him had described, albeit far from clearly, the reproduction of cells in the form of cell division, but these works were probably unknown to him until 1838.

The emergence of cells, according to Schleiden's theory, proceeds in the following way. In the mucus, which makes up the living mass, a small round body appears. A spherical clot consisting of granules condenses around it. The surface of this sphere is covered with a membrane - a shell. This creates a round body known as the cell nucleus. Around the latter, in turn, a gelatinous granular mass collects, which is also surrounded by a new shell. This will already be the cell membrane. This completes the process of cell development.

The cell body, which we now call protoplasm, was designated by Schleiden (1845) as cytoblastema (the term belongs to Schwann). "Cytos" in Greek means "cell" (hence the science of cells - cytology), and "blasteo" means to form. Thus, Schleiden looked at protoplasm (or rather, at the cellular body) as a cell-forming mass. According to Schleiden, therefore, a new cell can be formed exclusively in old cells, and the center of its emergence is the nucleus condensed from the grains, or, in his terminology, the cytoblast.

Somewhat later, describing the emergence of cells in 1850, Schleiden also noted the reproduction of cells by their transverse division, citing the observations of the botanist Hugo von Mohl (1805-1872). Schleiden, without denying the correctness of Mohl's careful observations, considered this method of cell development to be rare.

Schleiden's ideas can be summarized as follows: young cells arise in old cells by condensation of a mucous substance. Schleiden depicted this schematically as follows. He considered this method of cell emergence from the cytoblastema to be a universal principle. He took his ideas, so to speak, to the point of absurdity, describing, for example, the reproduction of yeast cells. He looked at an image of yeast budding. Looking at this picture, there is now no doubt for us that he saw typical budding of yeast cells. Schleiden himself, contrary to the evidence, still argued that the formation of buds occurs only by merging into lumps of grains near existing yeast cells.

Schleiden imagined the emergence of the yeast cell as follows. He said that in the juice from berries, if you leave it in the room, after a day you can notice small grains. The further process is that these suspended grains increase in number and, sticking together, form yeast cells. New yeast cells are formed from the same grains, but mainly around old yeast cells. Schleiden was inclined to explain the appearance of ciliates in rotting liquids in a similar way. His descriptions, as well as the drawings attached to them, leave no doubt that these tiny mysterious grains from which yeast and ciliates are “formed” are nothing more than bacteria multiplied in the same liquid, which, of course, do not have , directly related to yeast development.

The theory of cytoblastema was later recognized as factually erroneous, but at the same time it had a serious influence on the further development of science. Some researchers adhered to these views for a number of years. However, they all made the same mistake as Schleiden, forgetting that, by selecting a number of individual microscopic pictures, we can never be completely sure of the correctness of the conclusion about the direction of the process. We have already quoted the words of Felix Fountain (1787) that the picture revealed by the microscope can simultaneously relate to very diverse phenomena. These words retain all their meaning to this day.