BIOLOGY. – From the Greek βίος “life” and λόγος “discourse, reasoning,” it is the science of life in its normal and pathological phenomenology. According to Treviranus (1776–1837), who first used the term, biology means: the study of the different forms assumed by organic life, of the different conditions and laws governing its existence, and of the causes determining its activity. With this original concept, the term is imbued with a vitalistic imprint, inasmuch as the ensemble of phenomena to which it refers are subject to forces not found in the inorganic world. Many biologists even today are convinced that while the organized organic world is subject to the laws of physics and chemistry, it is also governed by forces unknown to the physical world; others, however, believe that the “vital” forces are obscure and seemingly metaphysical, but that with the progress of science they too will be evaluated according to the same laws as the physical world. This materialistic current of thought finds in Lamarck one of its earliest advocates.
The term biology can be used in a broad sense, according to the definition given, as well as in a strict sense, namely as the study of the habits and way of life (ecology) of various animals and plants. By general biology is meant a discipline that synthesizes all vital phenomena so as to discern the general laws that guide them. If we refer to one of the most modern treatises on general biology, for example that of Cotronei, we see that the material is divided into the following parts and chapters: Part I deals with “biological organization,” with chapters on the limits of biological sciences, mechanism and vitalism, the origin of life, the differences between animals and plants, the colloidal structure of protoplasm, the cell in general, the chemical constitution of organisms, the vital activities of cells, cellular and organismal reproduction, embryonic development, tissue structure, growth, old age, and death. Part II deals with “fauna and biological environments”; Part III with “morphology,” or the anatomy of living beings (in this book limited to vertebrates for didactic reasons), comparatively, so as to understand the value of structures.
The field of biology is vast, and accordingly various biological disciplines have arisen. First of all, we can distinguish animal biology, which concerns fauna, and plant biology, which concerns flora, although the division between the two kingdoms is not absolute due to the presence of living beings that represent intermediate conditions. Organisms can be studied from different perspectives: their structure, their activity or function, their anomalies. Thus we have three broad groups of disciplines, which we encompass with the terms general morphology, general physiology, and general pathology. Morphology includes cytology, which studies the cell; embryology, which studies the stages of development; histology, which considers the association of cells that constitute the tissues of multicellular organisms; organology, which studies organs; and anatomy, which studies the various parts of organisms. Particular disciplines include comparative anatomy, which investigates through the comparison of structure in various animal species the morphological value of various structures, and human anatomy, which deals exclusively with the structure of man. Physiology includes biophysics and biochemistry, which deal respectively with the physical and chemical aspects of vital functions; human physiology deals with the functions of man considered as an animal. Pathology, which treats abnormal and morbid processes in organisms, is distinguished into plant, animal, and human pathology. Human pathology is further divided into medical and surgical. One aspect of pathology is that studied by general pathology, which deals with the generic data of human morbid processes, such as the onset of processes, their phenomenology, the way they are distinguished and classified, the study of their course, the prognosis of their outcome, and the outcome itself. Disciplines related to it include bacteriology, which studies the life of pathogenic and non-pathogenic microorganisms (which do or do not cause disease); parasitology, which deals with organisms that live on other organisms, harming them and causing lesions; teratology, which investigates monstrosities, elucidating their embryological mechanism. Other branches of biology include zoological and botanical systematics, which deal with the classification of animals and plants into related groups; genetics, which deals with the transmission of hereditary traits and their behavior in descendants; ethology, which studies organisms in their environment (biogeography is a branch of it and studies the factors governing the geographical distribution of organisms); oceanography, hydrobiology, and limnology, which study life in the seas, in fresh waters in general, and in lakes in particular, respectively. Psychology should also be included among the biological sciences, at least in some of its aspects, specifically as experimental and comparative psychology, which study animal behavior.
A series of biological disciplines has a markedly practical character: agricultural biology, arboriculture or silviculture, horticulture, floriculture, plant pathology, agricultural bacteriology, agricultural embryology, hydrobiology applied to fishing, animal husbandry, poultry farming, sericulture, etc.
Finally, we can group all biological disciplines concerning the human species, such as anthropology, which deals with the various human races; human paleontology, which deals with fossil men; anthropometry; eugenics; human heredity; embryology; sociology; constitutional pathology; human psychology; and finally the entire group of medical sciences.
HISTORY OF BIOLOGY. – The study of biology begins in Italian schools in the 6th century B.C. From that time dates the first outline of a science that, while continuing to acknowledge the Divinity as the first cause of all things, investigates, on the basis of biological experiment, the secondary causes accessible to human study.
In this way speaks Alcmaeon of Croton, the first of the great "physiologists" (students of nature). With him begins anatomical investigation and the attempt to explain physiological phenomena. The first biological laws are formulated with the concept of *isonomia*, by which the organism is considered composed of various pairs of contraries, from whose proper proportion the normal state emerges, while from disproportion arises disease (monarchy). Contemporaneous, and in dispute over priority, is the principle of *enantiosis*, devised by Pythagoras. While the latter has a predominantly cosmic character, the Alcmaeonic principle is more directly biological. To Empedocles of Agrigentum (6th–5th cent. BC) is owed the specification of *isonomia* with the recognition of four elements (water, air, earth, and fire), which he calls "roots of all things." Even the animal organism would have such a constitution, and its various functions would be carried out by virtue of the magical law of similarity. Philolaus of Tarentum is credited with the fundamental principle of the correlation of the microcosm with the macrocosm. From Empedocles' principle of the four elements, the Hippocratic school developed the humoral concept, where the elements were replaced by humors (black bile, blood, phlegm, yellow bile). This theory laid solid foundations in biological thought, prevailing until the last century, while today it is revived in the theory of hormones. In it too, health consists in perfect proportion, while corruption or excess of one of them constitutes disease.
Aristotle is responsible for expanding the study of biology and establishing a doctrinal system; for which he was called the father of this science. His is the first attempt at a classification of living forms, where these, by degrees, starting from plants, through mollusks, arthropods, crustaceans, reptiles, and mammals, reach man. He founded comparative anatomy and is said to have been the first to execute anatomical drawings. He recognized the four Empedoclean elements, to which he added a "fifth essence." To him is owed, therefore, the principle of fusing science and philosophy within the same method of inquiry, which was to be replaced by the inductive method of Galileo; and likewise the establishment of the doctrine of spontaneous generation, a principle that was later misapplied and exaggerated (v. GENERAZIONE SPONTANEA).
Plant biology had its first student in Theophrastus of Eresus (4th cent. BC), a pupil of Aristotle. To him we owe a book on the *History* and one on the *Causes of Plants*. The study of biology reached its apex, as regards anatomy and physiology, in the Alexandrian schools (late 4th cent. BC), especially through the work of Herophilus and Erasistratus (v. ANATOMIA). Other noteworthy scholars, though earlier and therefore less advanced, were Diocles of Carystus and Praxagoras of Cos.
Biology occupies a large part in the *Natural History* of Pliny (23–79 AD). In it are exhaustively treated, for the time, botany, zoology, medicine, together with mineralogy, geography, etc. This work has the merit of having gathered together all that was known at the time. Contemporaneous is Pedanius Dioscorides of Anazarbus, author of a vast work on plants, animals, and vegetables, which he, however, considers only from the therapeutic side. From this work nearly all later authors who treated the same subject drew their inspiration (Pseudo-Apuleius, Macer Floridus, etc.).
Many Fathers of the Church also dealt with biology in order to glorify the divine creation, in their homilies and in their *Hexaemerons* (St. Ambrose, St. Augustine, Nemesius, etc.). Among these, St. Basil is important for his particular interest in scientific studies. Notable too are St. Hildegard, author of the famous *Physica*, and St. Isidore of Seville, author of the *Etymologies*; nor should the *Speculum Naturale* of the Dominican Vincent of Beauvais be forgotten, which is very interesting as it gives a picture of the knowledge in this field.
More important, however, for a principle of freedom of scientific thought is the work of St. Albert the Great, who also extended his biological studies, since he had the boldness to oppose his own thought to the assertions of Pliny, which were generally accepted dogmatically. Another student of biology, though directing his study of plants to their pharmaceutical uses, was Simon of Genoa, known as Simon of Genoa, chaplain to Boniface VIII, author of a *Clavis Sanationis*.
With the establishment of Renaissance thought, biology also received notable impetus. The renewed study of nature spurred scientists and philosophers to probe its mysteries, developing natural philosophy and the so-called natural magic, which may be considered a forerunner of the experimental method. Leonardo da Vinci, with his anatomical studies and observations in physiology and botany, deserves particular attention. He studied plant growth, discovered the law governing the emergence of leaves on branches, observed the concentric rings of the trunk by which the age of plants is determined, intuited the existence of a circulation in plants, experimented with the action of toxic substances on plant development, and obtained alcoholic solutions of chlorophyll.
In 1513 Leo X established the first chair of simples, to which Giuliano da Foligno was called. At the same time, a first *hortus simplicium* was formed in the Belvedere garden. Following the spirit of the Renaissance, a revision of ancient works was also undertaken in biology: important in this regard is the *De erroribus Plinii et aliorum* of Niccolò Leonceno. The first botanical gardens arose, in addition to that of Rome, the most famous being those of Pisa (1544) and Padua (1545). Venice is said to have had one as early as 1533.
Eminent scholars included L. Ghini, F. Bonafede, and the Anguillara (L. Squillante) for plant biology, systematics, and the distinction of new species; P. A. Mattioli, C. Durante, F. Calzolari, P. Castelli, B. Maranta, and F. Imperato for the same studies and for the pharmaceutical application of plants. Attempts were made at classification (M. Lobel—A. Cesalpino); to the latter we owe most important observations throughout the field of plant biology. A particular impetus to knowledge of the flora of the New World was given by P. Alpino, who described that of Egypt well, while among foreigners should be remembered J. Ruel (1479–1589) and C. de Lécluse (1526–1609).
In animal biology, the discovery of blood circulation by A. Cesalpino and R. Colombo was of the greatest importance. The humoral theory, however, remained unchanged (though attempts were made to modify it), and the functions of the various organs were still explained in terms of *virtutes*.
Of interest to zoology were the studies of U. Aldrovandi, while straddling the 16th and 17th centuries was the surgeon M. A. Severino (1580–1656), a scholar of comparative anatomy and a staunch advocate of the uniformity of the internal structure of all organized beings, which he believed differed only in external appearance. He extended his conclusions even to the plant kingdom. His *Zootomia democratica* should be regarded as the first treatise on comparative anatomy.
The study of embryology began in this period with the research of G. Fabrizio d’Acquapendente on the embryos of mammals and the chick.
In the 17th century, biological studies received further impetus. Apart from the iatrochemical and iatromechanical conceptions of the organism (v. PHYSIOLOGY), which respectively anticipated modern chemistry and physiological mechanics, biology in this century benefited both from new instruments that expanded the scope of investigation and from new institutions that enabled scientific studies, research, and experiments by providing scholars with the necessary material and intellectual resources. The most important instrument was certainly the microscope, whose invention is variously attributed to Jansen, Fontana, and Galileo. Other useful tools for this kind of research included the thermometer (whose application to the animal organism is due to S. Santorio), the pulsilogium (Galileo, Santorio), the hygrometer, the barometer, and so on. Also highly beneficial were the founding of scientific academies (such as the Accademia dei Segreti, the Accademia dei Lincei, the Accademia del Cimento, the Academia Naturae Curiosorum, the Académie Française, and the Royal Society).
The experimental method began to take firm root, promoted by Italian thinkers (Campanella, Bruno, Telesio, etc.) and established by Descartes, Bacon, and Galileo.
Among the leading biologists of this period were F. Redi, with his early systematic studies in parasitology, his first refutations of the spontaneous generation of insects, and his work on viper venom; M. Malpighi, the first scholar of general histology, discoverer of blood capillaries, cells, blood corpuscles, and those of the spleen, etc. His studies in comparative anatomy and on the incubated egg spurred further embryological research on plant anatomy. A. Vallisneri investigated insect reproduction (denying the spontaneous generation of gall insects) and described the anatomy of worms; D. Cestoni, who, together with G. C. Bonomo, discovered the acarine origin of scabies, also studied a wide range of biological and natural phenomena (algae, fungi, mollusks, amphibians, bats, etc.).
Among foreign scholars, mention should be made of G. Bauhin, recognized as the first systematist for his more consistent use of binomial nomenclature; J. Jung and J. Ray, who made attempts at zoological classification; and J. Pitton de Tournefort, an eminent botanist. G. Harvey completed the discovery of blood circulation and conducted studies on animal reproduction; J. Swammerdam made important anatomical studies on insects and their reproduction; Hooke carried out significant microscopic observations on the cell, while A. Leeuwenhoek discovered infusoria and devised special types of microscopes. He also described spermatozoa (already observed by G. de Hamme), thereby supporting the theory of preformationism against that of epigenesis.
Studies in comparative anatomy developed significantly in the 17th century, with figures such as G. Perrault, E. Tyson, N. Grew (to whom we owe the adoption of the term "comparative anatomy"), and G. Blaes, author of *Anatomie animalium*.
The 17th century in biology was marked by profound disagreements that foreshadowed more serious upheavals. Biology, as the "science of life," had deep repercussions in religious thought, and the 18th century was an era in which free thinkers, deists, and Christians clashed over their ideas; it was also the period in which the so-called philosophy of nature developed, offering a distinctive direction to scientific thought, while the first symptoms of the question of the origin of species began to emerge. Also notable in biology was the dispute between vitalists and mechanists (G. E. Stahl and F. Hoffmann).
In this period, C. Linnaeus published his *Systema Naturae*, in which plants and animals were classified. The system comprised classes, divided into orders, which in turn included genera, subdivided into species. The general plan of the system was established in 1735, with the definitive edition appearing in 1758. For each genus and species, he provided a definition using the same terminology. Opposed to the concept of systematization, which implied the idea of the fixity of species, was G. L. Leclerc, Count of Buffon, author of a monumental *Natural History* in which the first signs of Darwinian evolutionary theory can be found. His ideas were examined by Erasmus Darwin, the grandfather of Charles, who was to develop them further.
Comparative anatomy boasts the names of Vicq d’Azyr, who particularly studied the correlation of organs, and J. Hunter, anatomist, physiologist, surgeon, and paleontologist. L. Spallanzani established experimental physiology, refuted the spontaneous generation of infusoria, and conducted important studies on digestion, respiration, and other functions.
In embryology, G. F. Wolff emerged, giving this field a particular direction despite strong opposition from A. Haller, the great Swiss physiologist who formulated the theory of irritability.
The 19th century was the era in which biology reached its fullest development and acquired the name given to it by G. Treviranus. Comparative anatomy took its definitive direction with G. Cuvier and the formulation of fundamental principles by S. Geoffroy-Saint-Hilaire, who established his concept of organic unity. The greatest impetus to this science in the 19th century came from J. Müller, Owen, and Gegenbaur, though with differing approaches. Paleontology emerged as a distinct field, with R. Owen among its earliest exponents.
At the same time, the study of the origin of species began to take shape. In opposition to the idea of discontinuous morphology, the theory of evolution, first proposed by J. Lamarck, found support from Geoffroy-Saint-Hilaire but opposition from Cuvier, so much so that it seemed to fade away. Later revived by H. Spencer, the same concept (which came to be called evolution) gained its greatest impetus with C. Darwin, who based natural selection on the struggle for existence. Darwin’s idea was further developed by T. H. Huxley, who admitted the descent of man from animals.
Among those who saw in this theory a weapon to combat religion was E. Haeckel, who, however, did not hesitate to resort to stratagems when the facts did not support his views. To the principle of selection was later added that of C. von Nägeli (*Progression-gesetz*), who introduced the concept of idioplasm, as well as the theories of mutations (H. De Vries) and oligogenesis (D. Rosa). Despite considerable opposition (Flourens, C. Bernard, Pasteur, Quatrefages, etc.), evolutionism continued, with varying fortunes, up to the present day.
Modern genetics and heredity are connected to this field, which in turn links back to the early attempts of hybridists in the 18th century; their research culminated with the discovery of G. Mendel (1865), preceded by that of Ch. Naudin (1861). The study of living matter saw fundamental developments with the improved understanding of the cell, considered the basis of the structure of animal and plant organisms (T. Schwann, Schleiden, Bizzozero, Remak, etc.). The study of generation attracted passionate scholars, particularly in the field of artificial fertilization, already initiated by Spallanzani and later repeated by O. Hertwig and T. Boveri. The theory of spontaneous generation received its final blow from the experiments of L. Pasteur, which also disproved the spontaneous generation of microbes. A new field of study opened up in embryology thanks to C. von Baer, who, preceded by Rusconi, elevated ontogeny to an independent discipline. Experimental embryology began with the experiments of Baer and Remak and continued with those of Huxley and Agassiz, leading to Haeckel’s law (ontogenetic development recapitulates phylogenetic development), though true experimental embryology was established by G. Roux.
The great discovery of the existence of microbes, already intuited in previous centuries and demonstrated by A. Bassi in 1835, followed by L. Pasteur and R. Koch, founders of microbiology, greatly expanded the field of biological studies, extending them to invisible animal and plant forms. Similarly, physiology and paleontology benefited greatly from advances in auxiliary sciences and new concepts, particularly in physics and chemistry, as well as microbiology, while anatomy evolved its investigations and applications toward new directions (anthropology, constitutionalism, anatomy of the living, etc.).