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BIOLOGY


572


BIOLOGY


»mpounds into correlated structures, and to make

them active organisms.

Matter, then, can never, not even under the most favourable circumstances, produce either living cells or living biophorids, and hence we conclude that life owes its origin to God, the Creator of matter and energy.

Von Hartmann. Das Problem des Lebens (Bad Sachsa, 1906). 178; Ttndall. Fragments of Science; Bastian, Nature and Origin of Living Matter (London); Wasmann, Die Moderne Biologic und die Entwicklungstheorie (Freiburg, 1906), 182; Rosenthal, Allgemeine Physiologie (Leipzig, 1901), 552; Weis- mann, Vortrdge iiber die Descendenztheorie (Jena. 1904), 11,305; MncKERMANN in The Messenger (New York, April, 1900).

H. MUCKERMANN.

Biology (from /3ios, life, and Xi7os, reason, ac- count, reasoning) may be defined as the science on life and living organisms. It is essentially a science of observation and experiment and comprises the study of the structure, origin, development, functions, and relation to environment of plants and animals, discussing at the same time the causes of these phenomena. Biology is obviously divided into zoology (fvoi/, "animal") and botany (/Sordu), "herb"), according as the organism is either an animal or a plant. The biology of man is called anthropology (dydpoiTO! , "man") which, as far as it concerns man's body, is a subdivision of zoology. The science of insects is called entomology {(m-oixov, "insect"). Biology is not a science of yesterday, but is as old as the human race. Its main development, however, took place during the last centuries. As a result of this development a great number of daughter-sciences have sprung into e-xistence, each commanding its own more or less distinct field of research, and all united again to approach more and more the nature of life and to give us a clearer and more comprehensive idea of the variety and causes of vital plienomena.

An organism, be it plant or animal, may be con- sidered under a threefold aspect: either in its stmc- titre,OT in its functions, or in its development. And the science of biology is divided, correspondingly.

I. Br.\nches axd Subdivisions. — The science which describes the structure of organisms is called morphology (nop<j>^, "shape"). This may be either external or internal, and either simply descriptive or comparative. But in every case morphology con- cerns itself only with structure, in so far as this is a definite arrangement of matter.

External morphology treats of the size and shape of external parts and organs. Its chief purposes are, first, the identification of plants and animals according to certain systems of classification and, secondly, to facilitate the study of the functions of the various organs which it describes. It is prac- tically the same as systematic biology, which treats of the kingdoms, classes, orders, families, genera, species, and varieties of or^.anisms.

Internal morphology studies the interior structure of organisms and their parts; that is, organs, tissues, and cells. Accordingly it is subdivided into anatomy {dvaT^jivu, "cut up"), dealing with the gross struc- ture of organisms, histology {i<rT6s, "web"), with the minute structure of the tissues, and cytology (ki/tos, "cell"), with that of the cells, which are the ultimate structural and functional units of life.

Secondly, there are two sciences which refer to the functions, or activities, of organisms, according as these are performed by the single parts of the organism or by the organism as a whole. The latter science is called bionomics; the former physiology. Both physiology and bionomics not only describe and compare, but also inquire into the proximate causes of the various activities, and are thus intimately related to physics and chemistry, and at the same time are of paramount importance for the philosophy of life and of plant and animal activity. Bionomics


(sometimes called (ecology) observes how an organism acts with regard to its environment; that is, it de- scribes the mode of nutrition, dwelling-place (oixos), propagation, care of offspring, peculiar relation to certain classes of other organisms (symbiosis), geographical and geological distribution, and so forth. Physiology explains in detail how the single organs, tissues, and cells discharge their manifold functions, how a muscle contracts, how a gland pours out its secretion, and whether such functions are due to physical and chemical forces, whether and how far they are subject to a special directive.

Thirdly, the several biological sciences which de- scribe the development of organisms are comprised under the general name of morphogeny (jiapcp-f) and 7ewd, "origin"), or biogeny. The two branches of morphogeny are ontogeny {6vt — , participial stem, "being") and phylogeny (ipOXov, "race", "stock"). The former traces the gradual development of a single individual from the egg to the perfect being; the latter, that of the so-called "systematic species" from its ultimate ancestor, from which it is sup- posed to have been derived by evolution. Embry- ology is a special branch of ontogeny, and describes the gradual dififerentiation of the fertilized ovum until it has attained the structure peculiar to the particular organism.

Supplementary to the biological sciences above enmnerated is the science of palcecntology , which describes the fossil forms of plants and animals buried and petrified in the strata of the earth. The sciences of pathology, teratology, and numerous others, which pertain rather to medicine, cannot be considered here.

II. The Historical Development of the biologi- cal sciences may aptly be divided into four great periods: the first centring around Aristotle, Galen, and Albertus Magnus; the second commencing with Vesalius; the third, with Linnseus; the last with the theory of the cell, established by Schwann.

First penorf.— Aristotle (384-322 B. c.) laid the foundations upon which the magnificent edifice of biology has been constructed. His works, "De historia animalium", "De partibus animahum", and "De generatione animalium", contain the first scientific attempt to classify animals and to explain their various biological and physiological functions. Aristotle enumerates in his works about 500 kinds of animals. He distinguished groups (y^vv) from species ("Si), divided all animals into animals with blood iepatfia) and animals without blood (Avaifm), and again into eight principal groups, and thus established a system of classification which is still maintained, at least in a corresponding form, in our o\\ti days. He also knew many physiological facts, and made several discoveries in bionomics which were rediscovered only in the nineteenth cen- tury. The influence of the great Stagirite upon posterity was very great, and for nearly 2,000 years most students of biology were more or less satisfied. like the younger Pliny, to study and commentate the works of Aristotle. In morphologj' and physi- ology, however, a considerable advancement was made by Claudius Galen, who was born in A. D. 131. Galen was a Greek by birtli and later on a well-known physician in Rome. He was the first to define physi- ology as the science which explains the functions of the single parts (ttsrts partium) of an organism.

Together with Aristotle's works Galen's morpholog- ical and physiological teachings reigned supreme in all the schools of the Middle Ages till the time of Vesalius. Only among the princes of Scholastic philosophy were there any who stepped out of the narro%v circle of Aristotelean biology and commenced to study and interpret anew the living book of nature. We refer here mainly to the Dominican, Blessed Albertus Magnus (1193-1280) and to his pupils.