Zoology

ZOOLOGY, one of the sciences of the biological cycle, concerned with the study of animal organisms. The foundation of zoology as a science in its initial descriptive form was laid by Aristotle three centuries before the Christian era. In his "History of Animals," Aristotle not only provides external descriptions of many animals but also touches upon anatomy, the development of certain forms, and makes the first attempt at a classification of the animal kingdom, dividing animals into "blood-bearing" and "bloodless." The further course of Greco-Roman civilization is, in general, far from natural science and does not yield the names of major zoologists, except for some compilers like Pliny. The entire long period of the Middle Ages was also extremely unfavorable for the development of experimental sciences, so that zoology, after many centuries of stagnation, begins to develop normally and continuously only from the 16th–17th centuries. Initially, zoology advances mainly through the works of major anatomists—Vesalius, Eustachius, Fallopius, Fabricius—who, while developing mainly human anatomy, devoted part of their attention to various animals as well. To this same era also belongs Harvey's discovery of blood circulation. At this time, zoological research bears a rather mixed, encyclopedic imprint. At the end of the 17th century and in the 18th century, zoology enters the systematic period of its development, closely associated with the names of John Ray and Carl Linnaeus. By this time, in the hands of scientists, especially during the era of the great geographical discoveries, a huge but chaotic descriptive material on the fauna of various countries had accumulated, which required organization. The first attempt in this direction was made by J. Ray, who for the first time precisely formulated the concept of species and partly of genus, and also provided a brief system of animals based on anatomical characteristics. The work outlined by Ray was brilliantly developed by the Swedish naturalist Linnaeus. He introduced a strict binary nomenclature in the Latin language for designating each species of organisms, applied it to designate the majority of animals and plants known in his time, and provided a system of animals based on such essential morphological characteristics that it is partially preserved even now. Linnaeus divided animals into 6 classes: mammals, birds, amphibians (amphibians and reptiles), fish, insects, and worms. In his scientific worldview, Linnaeus was a strict adherent of the concept of the constancy of species. The very end of the 18th century and the first two-thirds of the 19th century are characterized by the flourishing in zoology of the comparative-anatomical direction, against the background of which the evolutionary doctrine gradually unfolds. Combining among the so-called natural philosophers (Oken, Carus, Goethe, and others) with a number of mostly groundless and fruitless hypotheses, comparative anatomy found a brilliant champion in Cuvier. Having mastered a huge amount of anatomical material, Cuvier establishes certain comparative-anatomical regularities, for example, the principle of correlation of organs, and also outlines 4 main plans of structure in the animal world, in accordance with which he divides all animals into 4 "branches" (embranchements): vertebrates, articulates, mollusks, and radiates. Cuvier applied his comparative-anatomical principles when studying the remains of fossil animals, bringing to life a new branch of zoological sciences—paleontology. Being, like Linnaeus, a defender of the theory of the constancy of species, Cuvier enters into a struggle with the evolutionary doctrine emerging at that time, represented among his contemporaries by J. Lamarck and Geoffroy Saint-Hilaire. Despite Cuvier's complete victory in his famous dispute with Geoffroy Saint-Hilaire, the evolutionary idea soon after Cuvier's death became guiding not only in biology but also in a number of other disciplines; it finally triumphed with the appearance (1859) of Charles Darwin's work "On the Origin of Species" (see Darwinism). Parallel to the development of theoretical questions, the time preceding and following the appearance of Darwin's famous work abounds with a number of major comparative anatomists, such as Huxley, Gegenbaur, J. Müller, A. Dohrn, and many others. In the early 19th century and especially in its second half, the center of gravity of zoological research shifts to the field of embryology, i.e., the study of the development of individual animals. In this embryological period, along with Baer (1st half of the 19th century), E. Haeckel, who formulated the biogenetic law, and the Hertwig brothers, who provided the theory of germ layers in the second half of the 19th century, one should note the brilliant works of Russian scientists—Mechnikov, A. Kovalevsky, Zalensky, and others. In the last two decades of the 19th century, another branch of zoology develops—experimental zoology, which is currently attracting great interest. This field, covering a large number of very different questions, deals with the influence of various external factors on the development and change of animals, studies general regularities in the course of the process of individual development (developmental mechanics), and is engaged in the investigation of phenomena of regeneration and transplantation, etc. The main representatives of this direction can be considered Roux, Barfurth, Child, Driesch, Herbst, Kammerer, Lillie, Loeb, Morgan, Przibram, and many others. Finally, from the very beginning of the 20th century, a new branch of zoological research grows—genetics, dealing with questions of heredity. Although the basic laws of inheritance of various morphological characteristics were discovered back in the 70s of the 19th century by Gregor Mendel, the latter's ideas did not initially receive wide recognition, and only in 1900 did the verification of Mendel's works by three prominent botanists at once (de Vries, Tschermak, and Correns) attract universal attention to these questions, after which genetics acquires a dominant significance among modern biological directions. Closely associated with the development of genetics are the names of Bateson, Johannsen, Nilsson-Ehle, de Vries, T. Morgan, and a whole number of others. From this outline, the circle of questions with which zoology deals is also partly clarified. The basis of zoology is formed by the so-called descriptive zoology, which considers morphology and anatomy, i.e., the general principles of the structure of animals, as well as histology, i.e., the microscopic structure of the organs and tissues of animals. Research in the same directions, but not of adult animals, but of successive stages of their development, falls to embryology. The study of the remains of fossil animals is combined under the name of paleontology or, more precisely, paleozoology, whereas the investigation of the distribution of various animal groups, not in time, but in space, on the surface of the earth, belongs to the field of zoogeography. Guided by the results of all the listed departments, zoology builds its conclusions regarding the systematics of animals, and also develops phylogeny, i.e., the doctrine of mutual kinship relations between individual groups. Finally, various kinds of experimental research are considered either in experimental zoology or, if they concern questions of heredity, in genetics. There is also a subdivision of zoology depending on the groups of animals over which research is conducted. Accordingly, one often speaks of mammalogy (study of mammals), ornithology (study of birds), ichthyology (study of fish), entomology (study of insects), etc. Finally, by combining questions of zoology that have any practical significance, one obtains applied zoology, medical zoology, etc.

V. Dogiel. Medical Zoology. The object of its study is all animals that have, at the present time, any medical significance in the broadest sense of this concept. The content of medical zoology has changed in different periods of history. It is undoubted that primitive man attempted to use parts of the bodies of various animals as medicinal agents. Therefore, it is natural that during the long and gradual historical process of the transformation of primitive medicine into scientific medicine, the latter initially inherited a multitude of medicinal agents of animal origin, the effectiveness of which was determined by the principle of post hoc, ergo propter hoc. Such agents, for example, were considered to be toads, scorpions, spiders, bats, pigeons, earthworms, bedbugs, lice, and others. Dung, urine, bile, blood, and other animal products were also used as medicines. Therefore, for a long time, the materia medica included information about various zoological materials. As an experimental basis was established for medical sciences, the 'pharmaceutical' bonds that connected zoology and medicine crumbled, and at the present time, only isolated species of animals remain that have some medicinal application (for example, blister beetles, musk deer, beaver, etc.). But instead of them, new, stable interests common to zoology and medicine have firmly established themselves; at the present time, zoology is no longer an 'explanatory text for apothecary material taken from the animal kingdom'; its significance is multifaceted; the content of medical zoology is determined by a) the utility that can be extracted from various animals in a medical (resp. sanitary-hygienic) respect, and b) the harm caused to human health by animals. The utility of animals for man in medical respects is as follows: 1. The use of animals or their products as medicines [Spanish fly (cantharidin), castoreum (musk)], the use (for now in the stage of development of the issue) of bee and snake venoms for the treatment of certain diseases. 2. The use of endocrine organs for surgical transplantation to humans; the use of these organs for organotherapy and the extraction of incretes. 3. The extraction of products auxiliary in the pharmaceutical business or used in other cases: tallow, lanolin, spermaceti, wax, silk, fish bladder, sheep intestines (catgut), bones for transplantation, etc. 4. The use of animals as 'factories' for the production of antitoxic sera and vaccines. 5. The use of animal products for dietary nutrition and treatment—white meat, fish, fish oil, liver, blood, etc. 6. Special forms of application of zoological disciplines in medico-sanitary and forensic-medical relations: a) determination of the purity of a body of water by the character of its animal population (see Biological analysis); b) the use of natural enemies against animals that are pests to human health to combat the latter (e.g., the breeding of larvivorous fish as a measure to combat malaria mosquitoes, see Gambusia); c) determination of the time of death by the presence of one or another animal (insects and mites)—destroyers of the corpse. The harmfulness of animals in relation to human health is determined by the presence of pathogenic animals in nature; such are: 1) external and internal, permanent or temporary parasites; 2) vectors of pathogens of infectious and parasitic diseases of humans; such vectors are for the most part various arthropods, both parasitic (for example, Anopheles and malaria) and non-parasitic (housefly, cockroaches, and others); 3) poisonous animals. Furthermore, important are a) intermediate and definitive hosts of parasites that also occur in humans; b) animal reservoirs of viruses (trypanosomiasis, spirochetosis, and others); c) animals that damage food supplies, warehouses (see Granary pests), furniture, clothing, linen; d) animals whose diseases can be transmitted to humans, etc. All these sections of medically interesting animals must find a place within the framework of medical zoology, as in their totality they determine its content. Practically, the scope of medical zoology is determined by the diversity of the fauna of a given country. The study of medical zoology has enormous significance both for the medical practitioner and for prophylaxis, and it is already possible to differentiate the difference in their interests in this discipline. The medical practitioner must be able to zoologically correctly identify the parasites of his patient (the accuracy of their identification must be as mandatory as similar requirements for bacteriological diagnostics), have a clear idea of the pathogenic properties of the parasites, and take into account their etiological significance in one or another disease. Finally, the medical practitioner must know the methods of expulsion or other measures to combat the parasite. The prophylactic physician, in addition, must be able to find harmful animals in the environment surrounding man and know both the paths of their spread and the measures to combat them. Medical zoology has broken down into specialties; first of all, parasitology stood out, which in turn is subdivided into protozoology, helminthology, and entomology, including in it the study of arachnids, i.e., arachnology. In the curricula of medical universities in the first year, there was, and in some universities still is, a course in zoology; however, it bears primarily the character of a purely zoological subject with a greater or lesser parasitological bias. It is impossible to give it the necessary specific character in the first year in full, as for the assessment of its special medical significance, students need to have preparation in the form of completed courses in bacteriology, pathology, and familiarity with clinical practice. Therefore, the most expedient is the teaching of a small course in special zoology (as preparatory to the course in general biology) in the 1st year and the organization of a special course in medical parasitology no earlier than the second semester of the 3rd year. In other medical universities, in accordance with new curricula, separate courses in zoology and botany are replaced by a course in general biology. If, at the same time, the teaching of medical parasitology is not ensured, a gap may arise between the parasitological requirements placed on the physician by life and that share of zoological preparation which he can receive in the university. Various branches of medical zoology are taught in schools of tropical diseases (London, Liverpool, etc.), courses at the Institute of Tropical Diseases (Hamburg), at the parasitological laboratory of the medical faculty in Paris, and many other places. In the USSR, the teaching of medical zoology is most secured in the Military Medical Academy, in the Kazan and Irkutsk universities, i.e., where a special course in parasitology has been introduced. Separate branches of medical zoology are taught in courses at the Tropical Institute in Moscow (protozoology, helminthology, entomology). Research work is connected with the zoological laboratories of the Military Medical Academy, some medical universities and physics-mathematics faculties, with tropical institutes, some microbiological institutes and malaria stations, with the Zoological Museum of the Academy of Sciences of the USSR and the Permanent Commission for the Study of Malaria Mosquitoes and Other Ectoparasites located under it, the Helminthofaunistic Commission, and other institutions (see Helminthology). The problems of medical zoology are addressed by the Russian Parasitological Society (Leningrad). The largest collection of objects on medical zoology in the USSR is the 'Museum of Pathogenic Animals' at the Department of Zoology in the Military Medical Academy. At the Tropical Institute in Moscow, a beginning has been made for a Museum of Tropical Diseases, which includes some objects on medical zoology.