Biology

BIOLOGY. Contents: I. History of biology. Vitalism and mechanism. - Emergence of empirical sciences in the 16th–18th centuries. - Emergence and development of evolutionary theory. - Development of physiology in the 19th century. - Development of cell theory. - Results of the 19th century. II. Modern problems of biology. Cellular physiology. - Successes of biological chemistry. - Application of physical chemistry to Biology. - Experimental study of vital phenomena in a living organism. - Modern psychology. - Developmental mechanics. - Development of evolutionary theory and genetics. - Prospects for the further development of biology. III. Applied biology. Application of Biology to medicine. - Application of Biology to technology. - Application of Biology to agriculture. - Eugenics. Biology (from Greek bios—life and logos—science), the study of life, a term used both in a broad sense, meaning the unification of everything known and knowable regarding life, and sometimes in a narrower sense as the science of the way of life. However, for the science studying the way of life of animals and plants in connection with environmental conditions, there is a more precise designation—ecology (oikos—dwelling, environment of life). At the present time, Biology is divided into a large number of special sciences, such as zoology, botany, morphology, physiology, systematics, ecology, etc. The study of life, which unites all these special sciences, can be designated as general Biology. I. History of biology. Vitalism and mechanism. Ancient history had one biologist—Aristotle (384–322 BC). He created a coherent, all-encompassing biological doctrine, which reigned supreme for two thousand years. It was also accepted by the Christian religion; churchmen for many centuries blindly adhered to it and considered any departure from it to be heresy. At the present time, millions of masses in different countries accept, in one form or another, perhaps without even suspecting it, Aristotelian Biology. Many humanist scholars are still under the spell of Aristotle's biology; and among biologists of the 20th century, voices are heard: "back to Aristotle" (Driesch). Aristotle not only used material more or less familiar to every observer (farmer, hunter, fisherman), but also observed much himself and, apparently, dissected animals. He combined this material into a coherent logical system. The basic features of Aristotle's logical thinking were, apparently, typical for the Greek race of his time; they are also widespread in our time. The basic element of cognition for Aristotle is the fact of his own subjective consciousness: figurative thinking and striving for a definite goal. He identifies this own soul—"psyche"—with life and transfers it to the external world, where the soul organizes dead, homogeneous matter. Every animal or plant consists of matter and soul, which gives matter form and purpose, just as a sculptor creates a statue of a definite form from homogeneous wax. Life is everywhere where there is form and purpose. It is in the air, water, and earth, and therefore living organisms can arise by themselves everywhere: mice and frogs arise from mud. Apparently, what modern physics calls force, energy, appeared to Aristotle (in contrast to "matter") as "vital force," a soul endowed with the ability to form purposeful shapes from matter; Aristotle calls this ability entelechy (from Greek en—inside, telos—goal, and echo—I have). Therefore, the limits of life for Aristotle appeared much broader than for the modern biologist, capturing even the inorganic world. To study organs for Aristotle means to guess their entelechy—purposeful designation, since form—the spiritual principle—is closely connected with the goal. Aristotle's physiological ideas are often primitively naive. He considers the hot heart to be the seat of the soul. The brain cannot be the center of the soul, as it is the coldest part of the body, and it only moderates the excessive heat of the heart. The significance of the kidneys, liver, and some other organs is outlined with great insight. However, in animals devoid of blood (insects), Aristotle for some reason finds no internal organs at all. Aristotle's dualistic doctrine of life is a complete philosophical system that developed from the primitive animism of primitive man, who also animates all objects of the external world. When, after the medieval period, the flourishing of science began again, biologists of the 16th–17th centuries (Caesalpinus, W. Harvey, F. Redi, and others) appear as followers of Aristotle and develop his doctrine. But at the same time, a new mechanistic direction arises—first in astronomy and physics (Kepler, Galileo), and then in biology. Representatives of this direction reveal a completely new type of logical thinking. They are all mathematicians and physicists. The starting point for them is the doctrine of quantitative relations between phenomena of nature. Where Aristotle saw only diverse, countless qualities of bodies, they strive to find only quantitative differences. A purposeful interpretation of natural phenomena does not satisfy them; to explain for them means to discover not goals, but causes of phenomena. In Biology, this method is carried out by R. Descartes (1596–1649). For Descartes, a living being is the same kind of natural body as others, and he compares it with a clock mechanism or with hydraulic installations that set in motion various machines and automatons that play different musical instruments and even pronounce words. He decisively separates the concept of life from the concept of the soul. For him, animals are only automatons, a very complexly constructed machine; only for man (paying tribute to the time) does he consider it necessary, according to the beliefs of the prevailing religion, to acknowledge the presence of a soul. Aristotle's entelechism and Descartes' causal mechanism are two sharply opposing views on life. Rarely is the opposition between thesis and antithesis expressed in such a definite form. The very methodological approach to the problem is sharply different in both cases. One might think that here there are not only two doctrines, two hypotheses, but two different types of human logical thinking. The explanation of phenomena by their purposefulness (entelechy) completely satisfies the logic of Aristotle, but it is not an explanation for the logic of Descartes, which strives to establish a causal connection of phenomena everywhere. In the 17th and 18th centuries, a revival of Aristotelian entelechism and vitalism is observed in the theories of Leibniz and, especially, Stahl (1646–1716, 1660–1734). The 19th century is characterized as the triumph of mechanism. But even in our days, when empirical biology has achieved enormous successes, both doctrines, or rather, both types of logical thinking, continue to exist side by side. In the history of Biology, these two currents play an unequal role. As our factual knowledge about vital phenomena deepened, and scientists mastered one or another vital process, i.e., learned to control them, these areas of Biology were entirely subordinated to mechanistic causal explanation. At the present time, only a few, most complex, biological problems, such as the phenomena of mental life and the history of the development of an organism from an egg, do not always yield to final causal analysis and allow a few modern vitalists to claim that not all vital phenomena can be reduced to causes of the same order that act in inanimate nature. But even in these areas, every year, with every new experimental work, the application of causal materialistic explanation expands and the possibility of speaking about its insufficiency narrows. Emergence of empirical sciences in the 16th–18th centuries. For nearly two millennia, the biological facts collected in Aristotle's books constituted the entire content of biology and were almost not supplemented by new research. Biology was a single science, and there was no need to divide it into parts. Moreover, it itself did not stand out as something separate from one general science—philosophy: both Aristotle and Descartes were philosophers, not biologists in the modern sense. The separation of biology and its dissection into separate sciences occurred gradually, due to the demands of practical life. First of all, medicine required familiarization with the structure of the human body. However, for a long time, physicians did not dare to dissect a human corpse; the anatomy of ancient times was based, mainly, on the dissection of animals. Only in the Renaissance was the fear of dissecting corpses overcome; physicians (most notably Vesalius, 1514–64), as well as artists (Leonardo da Vinci), who approached anatomy from their own point of view, began to compile atlases of human anatomy based on their own observations. If for artists the description of the form of various parts of the body appeared as the main and independent goal, then physicians inseparably connected with the description of organs attempts to understand the purpose of organs, their function. Therefore, medical anatomy from the very beginning stood in the closest connection with physiology, i.e., with the study of the vital functions of organs (physiology earlier also encompassed the concept of physics)."

One of the first brilliant discoveries of physiology was the establishment by the English physician W. Harvey (1578-1657) of the fact of blood circulation, which he observed and proved by means of experiments on living animals, introducing the method of vivisection into science. These experiments laid the foundation for inductive, experience-based (experimental) physiology, although for a long time after Harvey, biologists still used the deductive method to guess the functions of organs. The first experimental approach to the problem of the physiology of reproduction and development is also associated with the name of Harvey. He was the first to carefully trace the development of a chick from an egg and showed that the embryo develops from a part of the yolk. He further expressed the conviction, based on observations, that most other animals also develop from eggs. But the merit of the Italian physician F. Redi (1626-94) in this regard is especially great; he observed how flies lay their eggs on rotting meat, in which larvae develop from the eggs, later turning into flies. These observations dealt a heavy blow to the doctrine of Aristotle, which prevailed at that time, that flies and other lower animals (frogs, mice) are generated by themselves from dirt and silt. Little by little, in the following centuries, the fundamental tenet of modern Biology was established, that all animals originate from an egg—"omne vivum ex ovo"; the old doctrine of Aristotle on spontaneous generation was abandoned. The discovery of the microscope also dates back to the 17th century. It was first applied to biological research by the English physicist R. Hooke (1635-1703), who was the first to study the porous structure of cork with the help of a microscope and found that the latter consists of tiny chambers, to which he gave the name—cell (cellula). The doctrine of the cell, cytology (from kytos—bladder, cell), was destined to play a huge role in the Biology of the 19th century; at the present time, the cell is in our eyes the basis of all life. The Italian biologist M. Malpighi and the English botanist N. Grew (1628-94; 1628-1711) applied the microscope to the study of animal organs and plant structure. Microscopic anatomy was developed by them. Thanks to this, the ideas of biologists about the structure (or morphology) of organisms (from morphe—form) became significantly more complex. Leeuwenhoek saw spermatozoa in the sperm of animals and thereby opened the way for various theories of reproduction and fertilization; he and other amateur microscopists saw the microscopic population of water and thereby significantly expanded the boundaries of the living world. Swammerdamm (1637-80) wrote a huge work, which was published with numerous drawings only half a century after his death (in 1737) under the title "Biblia naturae," in which the structure and history of the development of a multitude of lower animals and especially insects are described. When studying the zoology of insects, the main attention was paid to their metamorphosis, way of life, and their instincts (in the 18th century, Reaumur). Linnaeus (1707-78), who laid the foundation for the scientific systematics of animals and plants, had a completely different, exceptional significance for this period in the development of biology. He met the urgent need for a system, which all biologists of that time keenly felt. Already in the 16th century, curiosity cabinets were set up in many cities, later turning into museums, where various rarities were collected, including natural history objects. There were also many private amateur collectors, especially since overseas countries were discovered. A practical need arose to systematize these collections so that one could make sense of them. In particular, medicine, which made extensive use of herbal treatment, urgently required their rapid identification. Linnaeus created a complete system of classification of the plant and animal kingdoms, which immediately came into general use and in its main features retains its significance for our time as well. Linnaeus was, in the literal sense of the word, a born systematist. He was little interested in abstract philosophical questions, did not conduct experiments, but arranged all his books, articles, welcoming speeches, and, probably, all his thoughts according to a pedantically constructed system, dividing them into categories of higher and lower orders. Linnaeus first of all established the concept of the species as the basic systematic unit ("We count as many species as there are different forms of animals and plants created in the beginning"). Since that time, the view of biologists on the origin of species has changed greatly, significant variability within a species has been established, but the concept of the Linnaean species, as an aggregate of more or less homogeneous forms connected by common origin and freely interbreeding, remains in force and is the basis of modern systematics. Linnaeus united groups of similar species into the concept of genera and introduced a double nomenclature to designate a species: from the generic and specific names. Linnaeus unites similar genera into orders, similar orders into classes. These groups of a higher order appear to him as artificial divisions, carried out for the convenience of classification and the determination of species—the really existing units. The end of the 18th and the beginning of the 19th century are characterized by the development of comparative morphology (anatomy). Already at the very emergence of human anatomy, doctors who avoided dissecting human corpses had to use the corpses of animals, in particular monkeys (Galen). In the 17th and 18th centuries, zoological gardens arose, in which large exotic animals were collected, and biologists working at these gardens received the opportunity to dissect and describe a large number of diverse animals. Comparative anatomy of animals reached a high level of development at the beginning of the 19th century thanks to the works of G. Cuvier (1769-1832). He develops the view of morphology as the geometry of organisms. For each of the four types of the animal kingdom he established, he also establishes a general plan of structure. In various classes, orders, etc., this type undergoes changes, but these changes are connected by the laws of the correlation of parts. For example, one or another change in the teeth of mammals entails a corresponding change in the structure of the limbs. In many cases, by the structure of one single part, e.g., a tooth, it is possible to determine the structure of the skeleton of the limbs, etc. Cuvier's vast experience in the field of comparative anatomy, especially of vertebrates, allows him to apply his knowledge to the study of the remains of fossil animals. Cuvier was the first to show with complete clarity that they differed sharply from modern ones. The rapid development of construction in Paris following the revolution allowed him to collect a large amount of material on fossil remains from the Paris suburbs. Thus, a new biological science arose—paleontology, i.e., the science of ancient extinct organisms. The emergence and development of evolutionary theory. The end of the 18th and the first half of the 19th century are periods of intensified collection of facts, especially in the field of systematics and comparative morphology. The slogan of this era is: nommer, classer, decrire—to name, classify, and describe. Instead of the philosophers who dominated until this time, striving to give a complete system of Biology as a part of general philosophy, numerous scientific specialists appear: zoologists and botanists, systematists, morphologists, physiologists, and embryologists. Most of them are pure empiricists who do not want to deviate from collecting factual material in the direction of rationalism. However, at the end of the 18th and the beginning of the 19th century, predominantly in Germany, a group of natural philosophers emerges who, in contrast to the prevailing purely empirical trend, strive to rationalize (make sense of) the phenomena of nature (Kant, Fichte, Schelling, especially Goethe and L. Oken). It is characteristic of the natural philosophers that they themselves hardly engage in observations and experiments and, although they use the factual material established by other researchers, they pay main attention to the logical development of their biological ideas, which often take the form of poetic fantasies for this reason. Goethe develops a theory about the unity of the plan in the structure of the organs of various plants—leaves, petals, and stamens of a flower—and simultaneously with Oken establishes the metameric theory of the structure of the bony skull of vertebrates, which supposedly falls apart into the same segments, metameres, as the bony vertebrae in the torso. These theories meet with sympathy among empirical biologists, and for half a century, the metameric theory of the bony skull is a favorite topic of comparative anatomical works. One might think that the development of comparative anatomy and paleontology, in connection with theorizing about the unity of the plan of the structure of organisms, should have led to the establishment of unity of origin and to the evolutionary idea. However, this did not happen; the majority of biologists until the middle of the 19th century firmly adhered to the biblical teaching about the creation of the world and individual animals and plants. In the second half of the 18th century, the French biologist Buffon paints a picture of the gradual emergence of animals and plants on Earth during a long period of its existence and gradual cooling (this period, contrary to biblical tradition, he calculates at 65,000 years).

He considers it possible to assume that the first pairs of all animals and plants (including even such highly developed animals as elephants), under certain conditions, arose by themselves from organic molecules scattered in nature in the same natural way as crystals precipitate from a solution. But all these views were discarded when it was recognized that organisms develop only from eggs or inside parents like themselves. At the end of the 18th century, the English physician Erasmus Darwin, grandfather of the great Charles Darwin, in several poetic works sketches a number of fantastic thoughts regarding the transformation of some species of organisms into others, but his poems do not attract the attention of biologists. In 1809, the French botanist, meteorologist, and physiologist Lamarck publishes the book 'Philosophie zoologique,' in which the evolutionary idea is expressed in a clearer form. He definitely speaks out for the fact that species are the same conditional systematic units as higher systematic groups—orders, classes, and types. Species change, but very slowly, so that these changes are imperceptible. Organic life has developed on earth for tens of thousands, perhaps millions of years; during all this time, organisms became more complex and perfected. Lamarck sees the reason for this development and perfection of animals in their strivings, which change and regenerate their bodies. Classical examples of this explanation by Lamarck are the following propositions: giraffes acquired a long neck because from generation to generation they reached for the upper branches of mimosas; the length of the legs and beak of storks is explained by the fact that they pulled them with difficulty from swamps, etc. Although Lamarck calls himself a materialist, there is no doubt that by the nature of his biological understanding he was a vivid vitalist; he recognized that a 'special force' acts in organisms, distinguishing them from non-living matter, and attributed to it an anthropomorphic ability to form, to change shape, an ability fully corresponding to the entelechy of Aristotle and modern vitalists. True, the majority of biologists contemporary to Lamarck willingly used the expression 'vital force,' but they, led by Cuvier, were predominantly empiricists, highly valued the accuracy of observations and experimental verification; in their eyes, all of Lamarck's interpretations must have seemed like arbitrary fantasies. It is not surprising that these fantasies attracted as little attention as the arguments of the German nature-philosophers. Geoffroy Saint-Hilaire (1772-1844) is considered, like Lamarck, one of the predecessors of C. Darwin in the history of the development of the evolutionary idea. With his name is associated the doctrine of the variability of species under the direct influence of external conditions, climate, soil, etc. But he also does not dwell in detail on this topic, does not attempt to substantiate his view with any precise and complete factual data and experiments. Like the nature-philosophers, to whom Geoffroy Saint-Hilaire was very close, he developed this topic rather as an abstract theoretical concept, was much more a theoretical morphologist, and wrote more about the plan of structure of animals and about the relationships of individual parts of the organism. His main idea was the unity of the plan of structure in the entire animal kingdom, in opposition to Cuvier, who asserted that for each of his four types there is a special plan of structure. It was on this ground that the famous dispute between Cuvier and Geoffroy Saint-Hilaire took place in 1830 at a meeting of the Paris Academy of Sciences. The latter defended the unity of the plan of structure of cephalopod mollusks and vertebrates, and Cuvier—the complete independence of both types. The winner in this dispute turned out to be Cuvier, and modern biologists must acknowledge his correctness, since the constructions of Geoffroy Saint-Hilaire were artificially fantastic. After the death of Geoffroy Saint-Hilaire, until the publication of C. Darwin's book 'On the Origin of Species' in 1859, the evolutionary idea completely disappeared from Biology. Two major German evolutionists of the 19th century—E. Haeckel and A. Weissmann, who went through the university school, state that they did not hear a single hint from any of their professors or senior colleagues during this period about the possibility of explaining the development of organisms through a natural process of evolution. On the other hand, in a scientific field adjacent to Biology, in the field of the study of the earth—geology—ideas close to the evolutionary doctrine developed little by little. Thanks to paleontological discoveries, it became clear as early as the beginning of the 19th century that during geological periods, faunas and floras replaced one another many times, gradually approaching modern ones. Cuvier, however, did not draw the conclusion from this about the gradual change of organisms. The history of the earth did not seem to him continuous, but divided into several clearly defined periods, which were separated from each other by world catastrophes like the biblical flood; each time after such a catastrophe, new faunas and floras were created at once by a creative force. This theory of catastrophe was dealt a blow by the book of C. Lyell, which appeared in 1830-32, who developed the doctrine of the gradual variability of the earth's surface through the continuous action of factors observed at the present time as well. From this, it seemed natural to conclude that the development of the organic world also occurred just as gradually, under the influence of natural causes, as the development of the earth's surface. But Lyell himself did not draw this conclusion; however, he had a profound influence on C. Darwin. Thus, although C. Darwin's book produced a revolutionary upheaval in biological science in the full sense of the word, undoubtedly the minds of biologists were already prepared for the reception of this revolutionary doctrine. It is not surprising that the evolutionary idea was published simultaneously by two English biologists—A. Wallace and C. Darwin: the former in the form of a short sketch, the latter in the form of a book containing a huge number of convincing facts collected by painstaking preparatory work over 20 years. C. Darwin showed, first of all, the incorrectness of the Linnaean concept of species as a homogeneous unit. Within each species, there are diverse groups, varieties; even individual specimens differ more or less sharply from one another. Along with this basic phenomenon of 'variability,' C. Darwin establishes another, equally basic phenomenon of 'heredity': the individual traits of children in most cases are more or less fully determined by the traits of the parents. The third Darwinian factor of evolution is 'natural selection.' The reproduction of organisms occurs very intensively; from one pair of parents come hundreds, and sometimes even millions of descendants, but under constant external conditions, only two from this huge number have chances to replace their parents, while the rest perish. The choice of those remaining for further reproduction is not accidental: all freaks, burdened with bad heredity, perish; the best remain, that is, the most adapted, transmitting their adaptability by inheritance to future generations. Since such a struggle for existence has been occurring on earth for many millions of years, it is natural that as a result of selection, species changed, split into new species, and selection ensured for each period the greatest adaptability, the expediency of organization. Using natural variability and heredity and applying the method of first unconscious, and then conscious artificial selection of producers, man has created and continues to create a huge number of the most diverse breeds of useful and beautiful domestic animals and cultivated plants. Man himself, as one of the last links in the development of the organic world, originated in the same natural way from his ape-like predecessors, with sexual selection being added to natural selection and the survival of the most adapted, so the strongest, most capable, and most beautiful men chose for marriage the strongest, most capable, and most beautiful women. The influence of Darwinism not only in biological science but also in all areas of human life was and continues to remain enormous. It dealt a decisive blow to many absolute religious dogmas and restructured the worldview of the broad masses of the population. It formed the basis of socio-economic and social doctrines and, above all, Marxism. Darwin's doctrine, after some struggle, was accepted by almost all biologists. Especially active propagandists of it were—in England T. Huxley, in Germany E. Haeckel, in our country K. A. Timiryazev and M. A. Menzbir. There were also scientific opponents—Agassiz, Quatrefage, Baer, Danilevsky, and others, but little by little they fell silent, and a period of full recognition of the evolutionary doctrine arrived. If at the present time there are scientist biologists who call themselves anti-Darwinists, then here, for the most part, we are dealing with objections against one or another particular proposition of Darwinism, which, naturally, had to change under the influence of the further development of science; other modern anti-Darwinists, like Driesch, are simply not interested in the problem of the historical process and put forward other tasks for Biology.

However, the struggle against Darwinism by opponents far from science, especially churchmen, has not subsided even to this day. In our time, especially in the least cultured states of North America, this struggle has greatly intensified. Darwin's teaching had a huge influence on the development of biological sciences in the second half of the 19th century. The entire field of comparative anatomy was reorganized, which now set as its goal, on the basis of a comparative study of the structure of animals and plants, to draw conclusions about their mutual kinship and to reconstruct the genealogical tree of the animal and plant world. Embryology—the study of the development of organisms—also achieved wide development. The foundations of embryology were laid even before Darwin by the works of Russian academicians K. F. Wolff (1679-1754) and K. E. von Baer (1792-1876); in this new, post-Darwinian period, Russian biologists emerged, especially A. O. Kovalevsky, I. I. Mechnikov, and V. V. Zalensky. Their works established that where the study of adult organisms does not reveal a kinship similarity between them, this similarity can be discovered by studying embryos and larval forms. E. Haeckel formulated the "biogenetic law" (see): the individual development of each organism repeats the stages of the evolutionary process through which the given species developed. The post-Darwinian development of paleontology also provided a firm support for evolutionary theory. Remains of ever new forms of animals and plants, representing important links in the evolutionary ladder of the organic world, were discovered and continue to be discovered. The Russian paleontologist V. O. Kovalevsky was the first to develop a method for studying paleontological remains from the point of view of evolutionary theory. The systematics of animals and plants were reworked on completely new foundations after Charles Darwin reorganized the old idea of the immutability of species. Evolutionary theory gave special interest to the geographical distribution of animals and plants, since facts from this field allowed conclusions to be drawn about the history of the dispersal of organisms in past times; Darwin believed that each species originated in one specific place on the Earth's surface. Ch. Darwin himself, in later works, extended his teaching to man and thereby laid the foundation for modern anthropology. In 1863, Lyell collected data, fragmentary at the time, on the finding of remains of fossil man, whose existence Cuvier had once denied. Since then, special attention has been paid to the deposits of the most recent, relatively recent geological period (diluvial, glacial); excavations in various places, especially in the caves of Europe, discovered numerous remains of man, somewhat different from the modern one, and next to them were found primitive stone tools, of more or less perfect workmanship, together with the bones of various animals (partly already extinct) that these primitive people fed on. They began to look for the remains of such fossil organisms that could be taken as intermediate links between man and his ancient ape-like ancestors; some finds were interpreted in precisely this sense (the Neanderthal skull, discovered shortly before the publication of "The Origin of Species"; the Krapina skulls, discovered in 1901; the discovery by the Frenchman Dubois on the island of Java of the remains of an "ape-man": Pithecanthropus erectus, etc.). The systematics of human races was also intensively studied, in which various anthropologists see either different genera, or different species of the same genus Homo, or varieties of one species Homo sapiens. Development of physiology in the 19th century. The problem of the historical origin of organisms, brought to the forefront after Darwin, does not, of course, exhaust all the scientific tasks of biology. Another most important problem of biology is the question of how vital phenomena occur at the present time and in what relation they stand to the physical and chemical phenomena of inorganic nature. At the beginning of the 19th century, almost until its second half, physiology had not yet been separated as an independent science. In universities, physiology was usually taught in medical faculties together with anatomy; the best physiologists of that time were at the same time, and even predominantly, anatomists (Bichat, Blumenbach, J. Müller, Purkinje, Milne-Edwards, and others), who concluded about the function of organs on the basis of their structure and did not strive to relate vital phenomena to physics and chemistry. Most of them showed a clear inclination toward natural philosophy and vitalism, recognizing the presence of a special "vital force" which is an exclusive feature of living nature. True, in the 18th century (1789-1790), the famous French chemist Lavoisier performed essentially important physiological experiments on the respiration of animals. He showed that the vital process of respiration is nothing other than slow combustion, the burning of the chemical components of the body with O of the air, during which CO₂ is released. Lavoisier managed to calculate the amounts of O inhaled by the organism and the CO₂ exhaled and to establish the quantitative laws of respiration, corresponding to the laws of chemical oxidation; he showed that the body heat of higher animals is the result of the same process of slow combustion, i.e., respiration. This dealt a heavy blow to vitalism, the doctrine of the isolation of living organisms among inanimate nature. Another blow to vitalism was dealt in 1828 by the German chemist Wöhler, who prepared urea artificially from inorganic compounds; vitalists believed that urea, like other organic compounds, is prepared in the organism under the influence of a vital force; Wöhler's brilliant discovery, which was followed by a number of other syntheses of the same kind, proved the complete incorrectness of this point of view. When, around the middle of the 19th century in the field of physics, after the works of R. Mayer and Helmholtz, the law of conservation of energy is established (long before this, outlined even by M. V. Lomonosov), this law is also extended to vital phenomena. From the middle of the 19th century, a brilliant era begins in physiology. In all cases where it is possible to apply the quantitative method to the study of vital phenomena, it is discovered that the metabolism and the change of energy, to the totality of which life is reduced in the eyes of physiologists, are subject to the laws of conservation of matter and conservation of energy common to all of nature. There is no room left for a special vital force, and vitalism completely disappears from the field of physiology. Little by little, all basic vital phenomena in animals and plants are reduced, at least in general terms, to physical and chemical phenomena. The creators of the new physiology are: in France—Magendie (1783-1855) and Claude Bernard, who wrote a magnificent book, also translated into Russian, "Phenomena of Life Common to Animals and Plants"; in Germany—E. du Bois-Reymond (1818-1896) and Helmholtz (1821-1894), both of whom used, predominantly, exact physical methods and introduced precise measuring instruments into physiology; they developed, predominantly, chapters on neuromuscular physiology and the physiology of the sense organs. Further, one must point out Liebig and Voit, who developed the doctrine of digestion; among those working on plant physiology, besides Liebig, Hofmeister, Sachs, Nägeli, and many others also stand out. In Russia, I. M. Sechenov, who laid the foundation for the study of the functions of the brain, and K. A. Timiryazev, with his works on chlorophyll (the green pigment of plants) and its role in plant nutrition, were especially prominent. All these physiologists of the second half of the 19th century were also supporters of the teaching of Ch. Darwin; this period is the period of the greatest flowering of the mechanical causal explanation of vital phenomena. Development of the cell theory. The development of the doctrine of the cell as the basis of vital phenomena should be considered the third great victory of biological science in the 19th century. In the 30s of the 19th century, the concept of the cell acquired broad significance. M. Schleiden, a German botanist who was for a time a professor in Dorpat, was the first to extend the doctrine of cellular structure to all plant structures, and T. Schwann, in his work "Microscopic Investigations on the Accordance in the Structure and Growth of Animals and Plants," published in 1839, broke down animal organisms into cells and tissues. But in the eyes of the first cytologists, the cell appeared as a very simple formation—a vesicle filled with liquid. For them, cells were only bricks from which the form of organisms is built. The main part of the cell seemed to be the membrane, which gives, especially to the plant cell, a definite external form similar to the form of a crystal. Like crystals, cells arise anew, precipitating from the juices of the organism, as crystals from a mother liquor. Little by little, the idea of the cell becomes complicated. In 1833, the English botanist Brown discovers a nucleus in the cell, which, according to further research, turns out to be a necessary constituent part of all cells. Conversely, the cell membrane, because of which the cell received its name, may be absent, and therefore loses its essential general significance. In 1863, M.

Schultze defines the cell as a lump of protoplasm equipped with a nucleus, in which all the vital phenomena of the organism take place. Initially, protoplasm, and with it the cell, was considered to be nothing more than a protein substance of complex composition. In the 1860s, it was assumed that chemists only needed to artificially prepare a protein substance to be able to create a living cell. But this simplified view was refuted by further research. Virchow established that a cell never arises anew, but exclusively through the division of cells similar to itself. This continuity becomes even clearer for the nucleus. The study of the patterns of reproduction—mitotic division of nuclei—leads to the conclusion of the extreme complexity of the nuclear apparatus, and consequently, of the cell. In the nuclei of animal and plant organisms, a specific number (from 2 to 48 and more) of microscopically small bodies is established for each species, which, for their ability to be stained by known dyes used in microscopic technique, received the name chromosomes (staining bodies). During cell division, each of these bodies is divided in the most precise manner into two halves. Various complex structures are also discovered in the protoplasm of the cell body. The cell turns out to be not a crystal-brick or a lump of protein substance, but a most complex organism. Parallel to the study of complex structures in the cells of higher animals and plants, the study of the life and structure of lower organisms is proceeding, which also turn out to be not simple, but very complex. Previously, they were called infusion animals (infusoria), assuming that they arose spontaneously in infusions of decaying substances. The brilliant research of L. Pasteur in 1862 showed that even the simplest single-celled organisms—bacteria—never arise anew, but only through the division of similar ones. The study of the process of fertilization, which in all animals and plants is reduced to the union of two cells—male and female—also played a huge role; in this process, the nuclei of both cells fuse, and the same (or almost the same) number of paternal chromosomes is added to the maternal chromosomes. The fertilized egg, with its complex of chromosomes, while possessing microscopic dimensions, contains within itself everything necessary for the development from it of a most complex organism of the same species and even with all the individual hereditary characteristics of a specific individual of that species. Numerous cytologists took an active part in the development of these cytological views during the second half of the 19th century: W. Flemming, Strasburger, O. and R. Hertwig, A. Weismann, O. Bütschli, Carnoy, Schaudinn, E. Wilson, S. G. Navashin, A. S. Dogiel, and many others. Results of the 19th century. By the beginning of the 19th century, biology still represented a unified science, and leading scientists could call themselves biologists in general, being simultaneously zoologists and botanists, physiologists, morphologists, and systematists. By the end of this century, biology had already disintegrated into a number of special fields, with their own separate tasks and their own research methods. Often, individual specialists no longer understand each other. A physiologist must work with the full arsenal of modern advances in physics and chemistry; higher mathematics becomes a necessary language for the quantitative study of vital phenomena, and this language is often incomprehensible to the morphologist and systematist; on the other hand, the greatest representatives of physiological science often lack the necessary knowledge from the fields of morphology, cell theory, and systematics. The gap between individual fields of biology is assuming threatening proportions and leads to the fact that individual biological problems, torn from neighboring fields, remain unresolved and seem insoluble given the current direction and methods of science. For many, especially not biologists, but philosophers not fully acquainted with the actual state of science, doubts arise at the end of the 19th century regarding the possibility of a causal mechanistic explanation of vital phenomena. Brunetière speaks of the bankruptcy of science, while the philosopher Bergson and the zoologist Driesch return again to the long-forgotten vitalism. The 20th century inherits the task of overcoming this scientific pessimism; modern biology is coping with this task, striving to unite the torn-apart scientific fields, working, mainly, in intermediate scientific areas and connecting physiology again with morphology, with chemistry, physics, and physical chemistry, and evolutionary theory with cytology and, through its mediation, with chemistry. Before our eyes, a unified general biology is being created again. II. Modern problems of biology. Cellular physiology. The brilliant successes of physiology in the second half of the 19th century were based, mainly, on the study of the physiology of organs and juices, fluids that are part of the living organism. Blood circulation and the movement of plant juices were reduced to the laws of fluid movement through tubes. The phenomenon of digestion in gastric and intestinal juices was reproduced as chemical reactions in flasks outside the organism. Electrical phenomena in muscles and nerves were studied; it seemed possible to bring the phenomena of irritability and the transmission of irritation along a nerve closer to the phenomena of the propagation of electric current along nerves. But when researchers tried to penetrate deeper into the essence of all these physiological processes, they encountered enormous difficulties. The theoretical models of the organs under study that they initially created turned out to be too simplified in comparison with reality. The cell theory, which was developing in parallel, clarified the reason for this failure. In the 20th century, the cell is no longer depicted as a simple lump of protein substance, but as a most complex mechanism in which all essential vital processes occur. Much in the structure of this cellular mechanism still remains unclear; a long series of years will pass before the problems of cell structure are clarified. But even now, with our knowledge of cell structure being far from complete, this information must be introduced into all physiological models. The physiology of the 20th century has become cellular physiology. A summary of the latest work in the field of cellular physiology is provided by Max Hartmann in his book "General Biology," published in 1925–27. Successes of biological chemistry. To study cellular physiology, it is necessary first of all to know the chemical composition of the protoplasm, nucleus, and other parts of the cell, as well as organic fluids, which are products of cell secretion. Knowledge about the chemistry of all these substances remains far from complete to this day; this circumstance is the main obstacle to a full physical-chemical explanation of vital phenomena. But still, the research of the last two decades has significantly advanced this knowledge. The brilliant work of E. Fischer, who studied the main products of protein molecule breakdown—amino acids—and developed a method for the synthesis of complex compounds close to proteins—polypeptides—played a major role. These studies showed that even a polypeptide consisting of 18 amino acids can yield a trillion isomers with the same empirical formula. This circumstance explains the greatest diversity of proteins and at the same time makes the task of analyzing individual protein compounds, and even more so their synthesis, practically difficult to accomplish. Meanwhile, a number of studies of blood serum of various animal species, as well as proteins of plants of different species, showed that each species has its own peculiar proteins and that the proteins of closely related species, for example, humans and chimpanzees, are more similar to each other than those of humans and lower monkeys, and even more so than those of a dog or other animals more distant from humans. Probably, the composition of each cell of each species of organism includes special proteins, but the possibility of subjecting each of these proteins to chemical analysis is still very far off. The chemistry of the 19th century established that only those chemical elements that are found in inorganic nature are part of organisms. Initially, organic chemistry dealt only with compounds consisting of C, O, H, N, S, P, and a few other elements. Research of recent years has established the important participation in the chemistry of living organisms of a long series of other elements found in nature and in organisms in completely negligible quantities, often not even amenable to chemical analysis. V. I. Vernadsky asserts that a large number of minerals found in the earth's crust (and, moreover, many rare minerals) have passed through the composition of "living matter." For the chemistry of the future, there is an important task to determine the participation in vital processes of all these elements, which has so far been barely touched upon by biologists. Biologists of our time have to work a lot, studying the participation in vital processes of such organic substances whose chemical composition is completely unknown, because they are found in organisms and are needed by them in such negligible quantities that they are completely inaccessible to chemical analysis. Physiologists of the 19th century were convinced that the animal organism needs only proteins, fats, carbohydrates, some inorganic salts, and water for nutrition.

Research of the last 15 years has established that, in addition, man also requires so-called vitamins (see) A, B, C, D, etc.—substances found in negligible quantities in natural food and often destroyed by food processing, for example, by heating. The second group of important biological substances, which also have almost not been successfully analyzed, are so-called hormones, contained in the blood of animals and secreted into the blood by living cells, predominantly by cells of special "endocrine glands." In the 20th century, a special science was created—endocrinology, dealing with the problem of hormones; hundreds of studies in this field are published annually. The third group of physiologically important substances of unknown chemical nature are "ferments," or "enzymes." These are substances, negligible quantities of which accelerate various physiological processes, just as spongy platinum, sulfuric acid, and other inorganic catalysts accelerate reactions between various substances that have no relation to living organisms. In the 19th century, Pasteur had grounds to assert that enzymes are a constituent part of living cells (bacteria, yeast). But since Buchner in 1897 isolated from yeast cells an enzyme producing alcoholic fermentation in solution, many more enzymes have been obtained in solution, and it is recognized that they are chemical substances, although not one of them has yet been isolated from solutions and subjected to chemical analysis. The fourth physiological group of substances, which are far from fully studied, are the poisons—toxins—secreted by pathogenic bacteria, and the antitoxins and other "immune bodies" arising in the blood under their influence. These substances have also been obtained in solutions, which can sometimes be diluted thousands and millions of times without destroying their physiological action, but only weakening it accordingly. The study of these four groups of substances, found in cells and their secretions in negligible quantities, constitutes at the present time a substantial part of biological chemistry (see). Obviously, the usual methods of chemistry are too crude to be applied to the study of these subtle chemical reactions. Application of physical chemistry to Biology. At the end of the 19th century, a new science emerged—physical chemistry, standing on the border between physics and chemistry and uniting the methods of these two sciences. Like physics, it relies to a significant degree on mathematics and strives to establish mathematical laws of chemical reactions, proceeding from the physical properties of molecules and their parts. It is interesting that the first foundations of this new science, even before the classical works of the physicists van 't Hoff and Arrhenius, were laid by the biologists Pfeffer and de Vries. One of the essential branches of physical chemistry—colloidal chemistry—developed in close connection with Biology, since the majority of substances in a living organism consist of colloids, and the cell, according to modern concepts, is a mixture of sols and gels (the two main phases of colloidal substances). Another branch of physical chemistry—the study of surface and capillary forces—is also most closely connected with Biology, since, thanks to cellular structure, surface contacts of various media are extremely developed in the organism, upon which capillary phenomena develop. It is not surprising that in the 20th century, biologists paid special attention to the application of physical chemistry to Biology. Excellent summaries of biological research in this direction are available in the book by R. Höber—"Physical Chemistry of the Cell and Tissues," in the book by Schade—"Physical Chemistry and Medicine," and in a number of books by Loeb; some of his books ("The Dynamics of Living Matter," "The Organism as a Whole," and others) are also available in Russian. Physical chemistry allows, first of all, an approach to the problem of the form of organisms. From the preceding, it is evident that since the time of Aristotle, form was considered an essential distinguishing feature of organisms, and modern vitalists emphasize the difficulty of a physicochemical explanation of form. On the one hand, modern physical chemistry establishes a definite form for atoms, which for the physicists of our time are complex "solar systems." Even more complex is the form of combinations of atoms—molecules, and especially organic molecules. If it were already possible to draw the shape of the molecule of the red blood pigment hemoglobin, then, of course, a picture would be obtained that would differ little in complexity from modern drawings of the best-studied unicellular animals. In any case, it is still far from the point where one could see anything similar to this complexity in nuclear chromosomes under a microscope, and the possibility is not excluded that the latter will turn out to be complex molecules of the most complex protein bodies. Research currently being conducted on the structure of solid organic substances (e.g., cellulose) by the method of Bragg X-ray lattices is gradually bringing us closer to such a conclusion. On the other hand, the form of the cell, which lies at the basis of the form of organisms, is now explained purely physicochemically—by the combination of liquid, mobile parts of protoplasm consisting of sols with solid skeletal formations consisting of gels—membranes, fibrils, rings, etc. (Koltsov). Each cell is represented, according to this principle, as a system combining within itself, like the drops in Plateau's experiments, mobility and the constancy of a definite external form. The abyss between the organized machine—the cell—and supposedly unorganized matter is gradually being bridged. Experimental study of vital phenomena on a living organism. Physiologists of the 19th century made relatively little use of vivisection and did not know how to conduct precise experiments on a living organism. In the 20th century, the methodology of such experiments has received wide development. Here, in the first place, one should place the brilliant works of I. P. Pavlov and his students. His first works were devoted to the study of the activity of digestive glands and were conducted on dogs, on which he learned to perform complex and delicate operations, preserving the lives of the animals for years and observing truly intravital phenomena. Only in the 20th century did they learn to conduct long-term experiments on organs removed from a living organism and continuing to live outside it. The Russian physiologist A. A. Kulyabko was the first to remove a human heart and, by passing a saline solution through it, observed its beating for hours and was able to conduct experiments with it. N. P. Kravkov, by passing a saline solution through the vessels of isolated rabbit ears and fingers taken from an amputated human hand or even from a corpse, became convinced that the vessels beat and retain their vitality, react to changes in salt composition, sometimes narrowing, sometimes expanding for many days after the start of the experiment; the nails of such fingers grow; by irritation, one can induce inflammation and the appearance of sweat in them. 20 years ago, another method for studying vital phenomena was developed—the method of tissue cultures. In a sterile environment, carefully avoiding contamination by bacteria, pieces of organs and tissues are taken and placed in nutrient solutions, blood plasma, etc. Individual cells and tissues begin to grow; under a microscope, one can observe how their growth occurs, how cells divide, and one can study the metabolism occurring within them. If the nutrient medium is changed, it is possible to maintain the life of a cell outside the organism for months and years. In the work of the American physiologist A. Carrel, to whom Biology owes the development of this method, cells taken from a chicken continue to grow outside the organism for more than 10 years—a period exceeding the maximum lifespan of a chicken. Another surgical method has received great development in recent years—organ transplantation. Until recently, biologists did not want to believe that an organ removed from one organism could be transplanted into another animal and take root there and begin to function. At the present time, such experiments are being conducted on a large scale and are yielding interesting results. Modern psychology. During the greater part of the 19th century, psychology remained divorced from Biology and was considered to be included in the circle of philosophical sciences, and in our country, it was taught in historical-philological faculties. Its main method was introspection. Of course, this subjective method of introspection is the only method for perceiving the peculiar phenomena of our own consciousness, but it is completely inapplicable to the perception of phenomena of the external world, and only by analogy with our own subjective experiences is the presence of consciousness attributed to other organisms that are physically similar to us; one is left completely at a loss when deciding the question—whether one should attribute consciousness to a monkey, a dog, a worm, an infusorian. In all ages, there have been psychologists who, like Aristotle, attributed to animals the same consciousness—will, feelings, and reason—as in man, and at the same time others who, like Descartes, considered animals to be machines and considered consciousness, the "soul," to be an exclusive feature of man. The 20th century can be proud of major acquisitions in this field as well. From various sides, approaches are being made to establishing an objective method for studying psychology. What is called psyche or mental life in the language of subjective psychology, modern biologists consider to be a system regulating the vital functions of the organism.

No machine not under continuous human supervision can operate without regulators that automatically bring the movements of its mechanisms into correspondence with changes in external conditions; it is natural that even among the simplest living organisms, including plants, one finds regulatory activity, irritability. During most of the 19th century, biologists considered the nervous system of animals to be the sole regulator of vital phenomena. Recent research has brought to the fore chemical regulation, which coordinates metabolism and energy exchange in plants and animals that do not possess a nervous system. With the appearance of a nervous system made of fibers connecting individual sensory cells and organs with muscles and glands, it takes upon itself the function of fine regulation of vital processes in accordance with changes in the external environment. But even in humans, chemical regulation plays a huge role, especially thanks to the development of various glands of internal secretion. Along with neuropsychic phenomena (from a subjective point of view: drives, feelings, temperament), the doctrine of chemical regulation of the vital activity of plant and animal organisms is developed by Max Verworn and, especially, Jacques Loeb, whose book "Forced Movements" was published in a Russian translation. Loeb develops a methodology for the experimental study of tropisms (drives) in relation to light, gravity, heat, chemical substances, etc.; in a number of cases, he succeeds in deeply penetrating the chemical nature of these regulatory processes, which are apparently independent or almost independent of the nervous system. As for the developed endocrine system of higher animals, in recent years in biology, the conviction is increasingly strengthening that these are organs that regulate metabolism and energy exchange through the hormones they secrete into the blood and which are carried by it. Some biologists believe that the time is not far off when it will be possible, by introducing certain substances into a person's blood, to induce feelings of pleasure or displeasure, fear, anger, sexual or other drives. Changing the temperament of animals was learned long ago, by turning, through castration, unruly bulls and stallions into phlegmatic oxen and geldings. As for the objective biological study of neuropsychic activity, the works of I. P. Pavlov and his school have played a huge role here. I. P. Pavlov studies the simplest reflex activity in dogs, following the path charted by I. M. Sechenov, but by a peculiar surgical method. Instead of studying how an animal responds to external stimuli with one or another more or less complex muscular movement, I. P. Pavlov chooses reflex responses from glands, especially salivary ones, thanks to which the task is significantly simplified and becomes accessible for quantitative determination. He distinguishes reflexes of two kinds: unconditioned (based, apparently, on innate nervous connections between sensory organs and salivary glands) and conditioned, in which such connections are established anew, during life, depending on experience. In the opinion of I. P. Pavlov, everything that is called rational activity in the language of subjective psychology—memory, learning, etc.—is, from an objective side, nothing other than complex, conditioned reflexes layered one upon another. American researchers Thorndike, Watson, Yerkes, and others approach the study of neuropsychic activity from another side. They set themselves the task of objectively studying the behavior of animals ("behavior"), which is why they received the name "behaviorists." In essence, they study, like Pavlov, conditioned reflexes, but not in salivary glands, but in complex muscular movements. The study of unconditioned innate reflexes and their more complex complexes, so-called instincts, has also moved forward over the last decade, with the term "instinct" having lost its former vitalistic shade. Here, the introduction by V. A. Wagner of the comparative method played an important role, with the help of which he reconstructs the gradual evolution of these "instincts" in exactly the same way as a comparative anatomist reconstructs the evolution of paired limbs or the skull of vertebrates. Mechanics of development. Complex as the mechanism of neuropsychic and chemical-psychic activity may be, there is a vital process of even greater complexity, even more difficult to subject to biological analysis. This is the process of the development of an organism from an egg. The fertilized egg, from which a human develops, is a microscopically small cell consisting of a protoplasmic body and a nucleus. The nucleus contains 24 pairs of chromosomes of different sizes and different shapes; half of them were in the egg before fertilization, and the other 24, forming pairs with the egg chromosomes, are introduced by the spermatozoon. From this egg, after a series of nuclear and cellular divisions, through the formation of germ layers, various folds, and with gradually progressing cellular differentiation, a child grows with all its most complex structures, including the organization of the brain and the entire nervous system. In what the complexity of the egg's structure consists is still almost unknown. It is possible that chromosomes represent extremely complex organs; perhaps these are huge protein molecules consisting of a series of amino acid links and other radicals, atomic groups, distributed in a row in an order specific to each species. Modern genetic experiments lead to such a view. It is possible that these atomic groups—parts of chromosomal molecules—separate from themselves into the protoplasmic body of the cell hormones or enzymes that accelerate certain chemical processes occurring during development. But all this is nothing more than hypotheses, and for now there are no methods for their verification. Meanwhile, observing the process of development, one cannot help but be amazed at its amazing regularity and expediency. It is as if something is leading, pushing the egg toward a definite goal, development into an expediently constructed embryo. Even the first accurate observer-embryologist K. F. Wolff spoke of an "essential force," of a "vital force" that directs development. Among modern biologists, H. Driesch adheres to the same point of view, who built his vitalistic theory at the end of the 19th century and became a prophet of modern vitalism, spreading his doctrine among biologists disappointed that the mechanistic doctrine does not provide a final resolution to life's mysteries. Driesch strives to uncover the main, in his opinion, mystery of life—the development of an organism from an egg—and does not find a way to resolve it by the causal method. Once a magnificent experimenter, in the 20th century he completely abandoned biological research, received a chair of philosophy in Leipzig, and eventually took up spiritualism. However, the majority of 20th-century biologists are completely unable to be satisfied with his vitalistic, teleological explanations. It was indicated above that it is still impossible to understand, even approximately, the complexity of the egg's structure, the individual parts of which in their size approach the size of protein molecules, the composition and structure of which also remain unknown. And meanwhile, in this organization of the egg cell must be contained all the typical characteristics of the species and even of the individual, since the smallest individual characteristics of the parents are transmitted by inheritance through the egg. It therefore seems completely natural that, precisely thanks to such ignorance and the almost complete impossibility of studying the physicochemical processes occurring during development, it is impossible at the present time to give any complete causal explanation for the development of an organism from an egg. But partially, individual phases of this process are gradually being clarified by a number of interesting biological experiments of the 20th century. A wonderful summary of these experimental data and hypotheses, attempting to give a causal mechanistic explanation for the process of development, is given by J. Loeb in his book "The Organism as a Whole." Proof that the causal explanation is yet to achieve brilliant victories in this field as well is provided by the experiments of Loeb and other biologists on artificial parthenogenesis, which have already become classic. Only quite recently, the process of fertilization was considered one of the most mysterious phenomena, providing fertile ground for vitalistic explanations. A. A. Tikhomirov was the first to show that unfertilized silkworm eggs can be induced to develop by irritating them with various mechanical and chemical methods. Jacques Loeb established a precise chemical methodology for artificial parthenogenesis. The term "mechanics of development" belongs to the German biologist W. Roux, who in a number of experimental and theoretical works tried to prove that a mechanistic explanation is fully applicable to processes of development as well. W. Roux founded a special journal in 1894: "Archiv für Entwicklungsmechanik der Organismen" (Archive of Developmental Mechanics); over 100 large volumes of this journal have already been published. Development of evolutionary doctrine and genetics. At the foundation of his doctrine, Ch. Darwin placed three phenomena: heredity, variability, and selection. However, all these phenomena were studied by him on the basis, mainly, of observations and theoretical considerations.

Only the 20th century introduced the experimental method into the study of variability and heredity and created a powerful science—genetics (from the Greek genos—origin), which united the greatest contemporary biologists. Charles Darwin was inclined to consider a significant portion of the variations in parental organisms as hereditary, regardless of how these variations were obtained by them: by inheritance from parents or during their lifetime, under the influence of external conditions, through exercise, etc. He even constructed an ingenious hypothesis of pangenesis to explain how acquired characteristics can be transmitted by inheritance. August Weismann, having come to the conclusion that germ cells, in their basic nuclear structure, represent exact copies of the fertilized egg, resolutely rose against the possibility of their transmitting any rudiments from body cells. He definitely denied the possibility of the inheritance of acquired characteristics and was the first to set up verification experiments, cutting off the tails of many generations of rats: this operation had no influence on the offspring. Since then, similar experiments have been conducted by many zoologists: Standfuss, Brown-Séquard, and especially Kammerer, who with great energy attempted to prove the Lamarckian principle of the inheritance of acquired characteristics. The doctrine of variability was transformed by the works of English biologists Francis Galton and his student Karl Pearson (Galton, Pearson), who based the study of variability on precise mathematical processing of material and linked the doctrine of variability with variation statistics. It can be said that Galton founded a new biomathematical science—biometry. Another difficult step in the doctrine of variability was taken by the Danish biologist Johannsen, who introduced a new research method—the study of pure lines, which is, however, accessible only for plants in which self-fertilization is observed. After a series of generations conducted through self-fertilization, a stable pure line with a fully defined hereditary composition is obtained—a real, hereditarily constant species, in contrast to the variable and, to the same extent as higher systematic categories, abstract "Linnaean species"; Johannsen (1903) considers the latter as a mixed "population" of individuals of diverse hereditary composition and pure lines, which interbreed to a greater or lesser degree. Plants belonging to one and the same pure line and possessing one and the same hereditary genetic composition can exhibit wide variability in experiments depending on the influence of external conditions, climate, soil, etc., but these "phenotypic" changes, or "fluctuations," are not transmitted by inheritance. Therefore, within the limits of phenotypic variability, natural selection is invalid; fluctuations are not transmitted by inheritance. This doctrine of pure lines has played a huge role in practical life and lies at the basis of modern breeding of cultivated plants. The doctrine of the non-inheritability of fluctuations and the invalidity of selection within pure lines has by no means shaken the evolutionary theory of Charles Darwin, but only strengthened it. In that population, a mixture of various interbreeding pure lines, which every Linnaean species represents, selection takes place between different genotypes, different pure lines. De Vries (1901), in his experiments with the evening primrose (Oenothera Lamarckiana) and other plants, showed that, along with non-inheritable fluctuations, saltatory hereditary variations—"mutations"—arise here from time to time. These are what lie at the basis of evolution; they are fixed or discarded by natural selection. Further research also clarified the cause of these saltatory changes in Oenothera, namely, accidental irregularities in the distribution of chromosomes, especially the doubling of the entire complex of chromosomes or individual chromosomes during the formation of germ cells—gametes. Gates (1915) collected extensive material showing that such mutations, which arose through a change in the number of chromosomes, served as the starting point for the formation of species in many genera of plants and animals. The doctrine of mutations expanded significantly when, around 1910, an intensive experimental study of the heredity of the small fruit fly Drosophila began, undertaken by T. Morgan and his associates in New York. This fly, being very undemanding, reproduces excellently and in 15 years has produced about 300 generations; for humans, the same number of generations would require about 10,000 years; it is understandable that such rapid reproduction under experimental conditions allowed biologists to penetrate much deeper into the causes of the evolutionary process than experiments on any other object—animal or plant. From the very beginning of the research on Drosophila, mutations began to arise from time to time—forms that had never been observed before in nature and which proved to be firmly transmitting their characteristics by inheritance. Up to now, the emergence of about 500 such mutations (or genovariations) has been registered; most of them were monstrous: flies with underdeveloped eyes or completely without eyes, with shortened wings or even completely without wings, flies with 4 wings instead of the usual 2, etc. But there are also fully viable breeds, for example, with eyes of the most varied shades or with a different body color. In most cases, the number of chromosomes in all mutations turns out to be the same—4 pairs. This means the cause of the emergence of mutations is different than in the De Vriesian evening primrose: deep hereditary changes occur within individual chromosomes, in the internal chemical structure of this or that chromosome, although it has not yet been possible to see these changes in a microscope. If the study of variability has been moving forward rapidly in recent years, the same must be said about the study of heredity. The first year of the 20th century was marked by an amazing discovery: simultaneously, three botanists—De Vries, Correns, Tschermak—discovered Mendel's long-forgotten research "On Plant Hybrids" (Mendel, 1865), verified it, and became convinced that Mendel's rule, which had gone unnoticed in its time, has the broad significance of laws of heredity. Through the crossing of certain individuals of peas, corn, and other plants, it was clarified that descendants receive by inheritance from their parents not a general resemblance to them, but individual rudiments, which can clearly manifest themselves in the form of more or less sharply striking characteristics (color of the grain, flower, dwarf growth of the plant, etc.). Hereditary rudiments, received by each organism from both parents, are combined on the basis of simple mathematical regularities, which were named Mendelian laws. Morgan and his associates, studying the heredity of Drosophila mutations, came to the conclusion that hereditary rudiments, or genes, represent material particles located in a strictly defined order along the length of each chromosome. With the help of counting segregations, as a result of crosses of different mutations, it is possible to determine in which chromosome and at what point in it the gene of the observed characteristic is located. It is possible that the gene is nothing more than a radical of a huge chromosomal molecule; in that case, the evolution of organisms reduces to the evolution of protein molecules, regulated by natural selection. Thanks to the development of genetics, Darwin's doctrine of evolution has been placed on the ground of precise experiment. Prospects for the further development of biology. As can be seen from the above, at the present time, we are still far from the final resolution of the fundamental problems of biology. The enormous successes of science over the last quarter-century have primarily emphasized that the biologists of the last century had too simplified a conception both of the structure of organisms and their constituent parts, and of their chemical composition and the physico-chemical mechanism of vital phenomena. But it is precisely the complication of conceptions that is a huge success: it explains the errors of our predecessors and ensures the great successes of the near future. Representatives of the materialistic trend, who do not recognize any explanation other than the causal one, can proceed with full confidence along the path they have chosen: all scientific discoveries have been until now, and, of course, will continue to be in the future, a victory of the materialistic trend. But it would be incorrect, from the point of view of the history of science, to deny any significance to the works of vitalist biologists: their main merit before history consists in the fact that they seek out the most difficult biological problems, for which a causal explanation seems to them inapplicable and where the conceptions of their contemporaries, who adhere to the mechanistic trend, turn out to be extremely simplified. And when the attention of the latter is directed toward these complex problems, one has to abandon unscientific simplifications; sooner or later, a causal explanation is found here as well. Biology is a living science; it does not stand still, it sometimes makes mistakes, but then it corrects its mistakes. Like any science, it moves, expands, and deepens. Sh.

Applied Biology. Since the time of primitive man, in whom elementary scientific ideas about life began to form, Biology has had as its purpose, first and foremost, practical tasks: to make life easier, to treat and prevent diseases, and to improve nutrition. Only during periods of cultural flourishing, when there remained time and energy for the luxury of abstract knowledge, could the study of theoretical Biology develop. But usually, the development of theoretical science was accompanied by the flourishing of its application to practical life. The successes of applied Biology have been especially great over the last 60-70 years, beginning with the great flourishing of theoretical Biology after the publication of Darwin's doctrine, the triumph of the physico-chemical direction in Biology, and the cellular theory. Application of Biology to medicine. Following the discovery of the cellular composition of animal and plant organisms, it was also applied to the doctrine of diseases, pathology. In Germany, R. Virchow developed the idea that at the basis of most diseases lie abnormal life processes in certain cells or tissues of the organism, and laid the foundation for cellular pathology. In the further development of this science, the doctrine of I. I. Mechnikov on phagocytosis and the comparative pathology of inflammation played a huge role. At the present time, the study of pathological characteristics of cells constitutes the most important chapter of pathological anatomy, and the entire doctrine of diseases, which makes wide use of the experimental method, represents a development of the physiology of the diseased organism. The treatment of diseases relies on pharmacology—the science of drugs, which is also a part of Biology and is based on the experimental study of the action of drugs on animals. The French biological school of Louis Pasteur played a huge role in the development of modern medicine. Pasteur developed the doctrine of the bacterial origin of infectious diseases, which, before our very eyes, has revolutionized the methods of combating epidemics. Thanks to this, a number of infectious diseases, previously considered disasters against which one could not fight, have now, when the biological foundations of their spread became known, almost disappeared in civilized countries. After it became known that the bacteria of typhoid fever, cholera, and dysentery are spread, mainly, by water, cities with well-constructed water supply systems ceased to be devastating centers of these epidemics; the final suppression of epidemics depends, mainly, on the success of the fight against dust and flies, which are also spreaders of contagion. Biology taught us further that the spreaders of typhus and relapsing fever are lice, and the spreaders of bubonic plague are rats, gophers, and other rodents, from which plague bacteria are transmitted through fleas. But Pasteur did not limit himself to the study of bacteria and their life processes associated with disease, but also established the main ways of fighting bacteria. He developed methods for weakening the poisonous action of disease-causing organisms and brilliantly applied this method to the weakening of the poison of chicken cholera, anthrax, and rabies. Later, Roux and Behring, modifying the Pasteur method, developed vaccinations against diphtheria. Then, similar biological methods of fighting tetanus, typhoid fever, cholera, dysentery, etc., were discovered. For a number of infectious diseases, the cause of the disease is not bacteria, but other microscopic organisms—Protozoa, which belong to the animal kingdom, and not to the plant kingdom, where bacteria are usually classified. In 1881, the French physician Laveran discovered in the blood of patients the causative agent of marsh fever—malaria, a terrible scourge of humanity, especially destructive in hot countries. Through the works of a number of biologists—Italian, German, and Russian—the complex life cycle of this parasite was gradually clarified. The Italian zoologist Grassi established that the only way for a human to be infected with this disease is the bite of certain mosquitoes, Anopheles, which themselves become infected from people sick with the fever. The same method of spreading contagion through mosquito bites was established for another scourge of humanity—yellow fever; this disease has now almost disappeared in Rio de Janeiro and other American cities, which were once almost continuously subjected to epidemics. The successes of Biology have had a huge influence on surgery. The discovery of chloroform (Morton, 1846) and other anesthetic agents made operations painless, and the discovery of bacteria and the development of methods for protecting wounds from bacterial infection (Lister, 1867) made possible such operations that surgeons had not dreamed of even a few decades ago. The successes of physiology in the 20th century also quickly found practical application in medicine. The doctrine of vitamins, which arose before our eyes, immediately made it possible to cope with two severe forms of diseases. It turned out that beriberi, a destructive disease that breaks out epidemically in countries where the population feeds almost exclusively on rice, is not a contagious disease at all, as was previously thought, but an "avitaminosis" arising due to a lack of vitamin B, which is contained in negligible but perfectly sufficient quantities in the rice husk, but is absent in polished rice. Factory polishing of grain spoiled a healthy natural food product. Even more significant is the discovery of the origin of scurvy, or scorbutus, which arises due to the absence of vitamin C, which is contained in vegetables, lemons, etc. A no less significant revolution is being produced in our time by the practical application of the doctrine of glands of internal secretion. Substances extracted from various endocrine glands, so-called organotherapeutic preparations, have become favorite medicines of modern physicians; every step forward on the path of improving the extraction of these substances is immediately used by practitioners. Numerous myxedema patients with insufficient thyroid gland activity can maintain their existence only by continuously consuming thyroidin. In mountainous areas, where goiter disease is widespread, schoolchildren take iodine universally, which is especially necessary, apparently, for the normal development of the thyroid gland. Just three years ago, insulin was isolated from the pancreas; already thousands of diabetics in all countries have saved their lives and continue to exist only thanks to constant injections of this preparation. In recent years, after the fundamental works of Brown-Séquard, Steinach, and Voronoff, the rejuvenation of the aging organism has come into wide use by acting on the weakened sex gland through ligation of the vas deferens in men or by transplanting to the patient a sex gland of the same sex from a human, monkey, or other animal. There is no doubt that the significant drop in mortality, which is observed in various countries and is progressing from year to year, should be attributed mainly to the development of medicine based on biology, which cures, and especially, which prevents. Application of Biology to technology. Humanity has long used various biological processes for technical purposes. Even primitive man made various microorganisms work for him, of course, without suspecting their existence. The preparation of sour milk, curdled milk, cottage cheese, and cheese, the preparation of dough and the baking of bread, the preparation of grape wine, vodka, beer, and other alcoholic beverages (up to and including Russian kvass), the preparation of vinegar and other acids—all these technical processes are carried out with the help of bacteria. Man noticed biological processes occurring in nature and adapted them to his needs, introducing various improvements based on experience. But from the time that Pasteur developed the methodology for preparing pure cultures of bacteria, a revolution occurred in all these industries. Pure cultures of bacteria specifically associated with various types of fermentation were isolated. E. C. Hansen applied the same method to the purification of yeast cultures, and little by little, all these technical industries were placed on a strictly scientific footing. Now all large factories of this kind are connected with scientific laboratories; work is carried out under the supervision of scientific biologists. The supply of water to cities and the purification of sewage, so important from the point of view of modern city improvement, are also in the hands of biologists (see Biological method of sewage purification). Continuously with the development of science, methods for freeing water intended for drinking from disease-causing bacteria are being improved, and on the other hand, methods for the rapid purification of sewage water through the work of bacteria and other organisms on irrigation fields and on biological filters. Bacteriology also produced a revolution in the processing of food substances. The same methods by which Pasteur, in his scientific experiments, freed his cultures from bacteria are also used for the preparation of canned goods, which has grown into a series of diverse technical industries. Application of Biology to agriculture. Agriculture has been completely transformed since the plant physiology of the 19th century clarified that a plant, like any organism, needs food and, first of all, mineral salts, which it obtains from the soil.

Methods of soil fertilization were introduced, in addition to manure, which had been used since primitive man, also mineral fertilizers: nitrates, potassium salts, calcium, sulfates, phosphates, etc. A huge role was played by the discovery that microorganisms develop on the roots of leguminous plants, possessing the ability to assimilate nitrogen from the air; clover and other leguminous plants were introduced into crop rotation as green manure. Vinogradsky's research on nitrifying soil bacteria, which convert ammonia compounds into nitrates, made it possible to enrich the soil in this way as well with substances that are assimilated by plants. These biological discoveries allowed, in civilized countries, over a period of a few decades, to increase crop yields by 100% or more. The successes of physiological chemistry had a corresponding influence on animal husbandry. The feeding of domestic animals, previously carried out intuitively, by tradition, became a science. The chemical composition of feed substances was studied, their nutritional value was determined, and where animal husbandry is conducted rationally, every liter of milk and every kilogram of meat costs much less. The breeding of cultivated plants and domestic animals was transformed under the influence of the successes of genetics. Especially clear progress, thanks to the development of genetics, was marked in plant cultivation. The method of selecting pure lines made it possible to obtain new varieties of very valuable cereals and other agricultural plants. For example, some varieties of wheat, which received wide distribution in Canada thanks to their drought resistance, were bred experimentally, in the form of pure lines, from a single selected ear. Over the last quarter of a century, selection stations have sprung up all over the world, setting the practical task of breeding and purifying new cultivated varieties. It turns out that the selection of appropriate seeds, even without expensive land reclamation measures for tilling and fertilizing, can sometimes immediately increase yields by tens of percent. In view of the great difficulty of studying the genetics of domestic animals, especially their productive properties (milk yield, egg production, etc.), the practical application of genetics here has yielded fewer striking results. But still, new breeds of cattle have been created; cows of these breeds give, on average, up to 165–245 kg of milk fat per year (instead of the usual 33–66 kg), and individual specimens even over 800 kg. Chickens have been obtained that give, on average, up to 200 eggs per year, with the egg production of individual representatives exceeding 300 eggs, etc. There is no doubt that in the near future, thanks to the refinement of our knowledge of genetics, even more significant successes will be achieved here. The fight against diseases of plants and, especially, animals has changed under the influence of the successes of Biology to the same extent as medicine. It is sufficient to point out that such a large branch of South European industry as sericulture, which in the 60s of the XIX century stood on the brink of complete ruin due to the development of the devastating contagious disease pebrine, was saved by L. Pasteur, who discovered the microbe of this disease and indicated methods of fighting it. Eugenics. The evolutionary theory showed that man is only one of the representatives of the animal kingdom. Modern physiology finds no essential differences between the vital processes occurring in man and in other animals. Genetics studies the heredity of individual traits that distinguish people from one another. At the beginning of the XX century, the idea arose about the possibility of rationalizing human reproduction with the goal of protecting the human race from the possibility of degeneration and, by selecting the most valuable producers, improving the human breed just as the breeds of domestic animals and cultivated plants are improved by artificial selection. F. Galton at the beginning of the XX century gave this new applied science the name 'eugenics'. 'Eugenics is,' he says, 'a discipline that studies which factors improve and which factors worsen the mental and physical qualities of offspring.' The new eugenic movement is spreading widely in different countries; eugenic societies and journals are springing up everywhere. In some countries, practical measures are already being implemented or discussed for the sterilization of idiots and other extreme degenerates by means of a surgical operation, which, without affecting health or even sexual life, nevertheless deprives one of the possibility of having offspring. On the other hand, propaganda is being conducted for the increased reproduction of especially valuable and healthy individuals, which is strongly reduced due to the social conditions of modern life. Of course, all these measures do not at all resolve all eugenic questions, but it is undoubtedly true that the task of improving the human breed is the most valuable dream of humanity, and its achievement is impossible without further successes of biological science (see Eugenics).