Respiratory Organs

RESPIRATORY ORGANS. Contents: Comparative anatomy of R. o..........614 Pathophysiology of R. o........619 Statistics of diseases of R. o..............625 Comparative anatomy of R. o. In invertebrates, R. o. are developed differently depending on the degree of development of the circulatory system. In Protozoa, respiratory gas exchange occurs either osmotically, over the entire surface of the body, or is associated to a certain degree with the activity of contractile vacuoles. In sponges (Porifera), which lack a specialized circulatory system, gas exchange occurs in the body cavity and in the channels and chambers connected to it. In coelenterates (Coelenterata), gas exchange is associated with the gastrovascular system, which primarily carries digestive functions. In echinoderms (Echinodermata), respiration is associated with the ambulacral system, which primarily carries hydraulic-motor as well as excretory functions, and in sea urchins, special ambulacral gills differentiate for respiratory purposes; in starfish, special gill sacs are associated with the ambulacral system; in holothurians, respiration is carried out by the tentacles, which contain branches of the ambulacral system and so-called lungs, which are appendages of the hindgut. Enteropneusta have a special gill section, which is a continuation of the intestine and is penetrated by gill slits. - In flatworms (Platyhelminthes), which have neither a circulatory nor any other vascular system, gas exchange occurs through the skin, as in roundworms (Nematodes) and rotifers (Rotatoria), which have neither a circulatory nor a respiratory system. Annelids have mostly a closed circulatory system, and in some cases also special R. o. in the form of external gills, which are highly vascularized appendages of parapodia-lateral body protrusions used for movement, or paired outgrowths. In most annelids, respiration occurs directly through the skin. In mollusks (Mollusca), R. o. are represented by gills, which in bivalve mollusks lie in the mantle cavity (ctenidia, or primary gills); in gastropods, secondary gills in the form of paired outgrowths are also found. In some gastropod mollusks (naked slugs), a special lung differentiates, which is a modification of the mantle. Finally, in snails of the genus Janella, there is a complex tracheal cavity, opening with a special opening on the back and representing a system of blind tubes surrounded by a subcutaneous blood sinus. There are mollusks without specially differentiated R. o. that breathe through the skin. Crustaceans (Arthropoda) mostly breathe with gills, which are plate-like appendages of the legs; in large crustaceans, e.g., in the river crayfish, these appendages are also present on the thoracic legs and are hidden under the carapace, forming a more or less closed gill cavity, and in some crayfish this cavity is lined with a villous membrane and functions as a lung. Many small crustaceans lack gills and breathe through the skin. Arachnids (Arachnoidea) breathe with lungs in the form of skin pockets, divided by hollow plates, inside which blood circulates (scorpions, spiders). In many arachnids (solifuges, pseudoscorpions, mites), there are more or less branched respiratory tubes-tracheae, opening to the outside by stigmata. Insects (Insecta) breathe exclusively through tracheae, lined with a chitinous layer forming spiral thickenings. The tracheae of insects open on the sides of the body segments through paired breathing organs-stigmata. Adjacent stigmata are connected by longitudinal tracheal anastomoses, forming two lateral trunks connected by transverse branches. The finest branches of the tracheae form a dense respiratory network in the insect's body. In some insects, the tracheae are connected with air sacs that play a role in flight. Amphioxus breathes with the help of a gill cavity, equipped with gill slits and lined with ciliated epithelium.

Einstein. In vertebrates, the main organs of aerial respiration are the lungs, and the organs of aquatic respiration are the gills. Both develop in close connection with the anterior part of the digestive tract. It is especially characteristic of vertebrates that a paired series of so-called gill slits develops in the pharyngeal region, connecting the anterior intestine with the external environment. In terrestrial vertebrates, these slits exist only in the embryonic state, indicating their origin from aquatic forms; in lower, water-living vertebrates, such as cyclostomes and fish, the actual gills develop in these slits. The number of slits in cyclostomes can reach 14 pairs, but in most fish it is limited to 5 pairs, which in lower forms open as separate gill openings directly to the outside, while in ganoid and bony fish they are covered by the gill cover. The actual gills are extremely complex structures consisting of numerous leaflets located on both sides of each gill slit on the gill septa, supported by their internal skeleton—the gill arches. The gills are supplied with venous blood by means of paired branches of the ventral aorta—the afferent gill arteries. The latter pass along each gill septum, arching around the gill region of the pharynx, and give off branches to the gill leaflets, which break down into an extensive network of capillaries. The oxidized blood is again collected in each septum in the efferent gill artery. The latter connect with each other to form the dorsal aorta. The complexity of the structure of the gill leaflets finds its explanation in the need to maximize the respiratory surface. The mechanism of respiration varies in different fish. In any case, water usually enters the pharynx through the oral opening, protected by folds of the mucous membrane that function as valves. In cartilaginous fish (sharks and rays), water often enters through the first visceral slit—the spiracle, protected by a special valve. The suction of water into the oral cavity occurs as a result of the active expansion of this cavity by the action of a series of muscles (especially the muscles that raise the hyomandibular apparatus), as well as due to the suction action of the gill cover when it is raised (whereby the membranous edge of the cover functions as a valve). Water is pushed out through the gill slits to the outside when the oral cavity contracts and the gill leaflets are closed. In addition to the internal gills described, branched external gills also develop in the larvae of some fish (especially lungfish) and in the larvae of amphibians, located in the same area on the outer wall of the gill septa. In some fish, especially in tropical freshwater forms, various additional respiratory organs exist, the development of which is explained by the low oxygen content in the water at high temperatures, as well as the periodic drying up of bodies of water. Additional respiratory organs in fish are usually connected with the main ones, representing for example outgrowths of the gill cavities, the surface of which can be increased by the formation of folds ( labyrinth fish). Sometimes such outgrowths form long paired sacs extending backward along the spine (in some catfish). Bony ganoids and lungfish can swallow air into another unpaired or paired sac-like outgrowth of the intestine—the swim bladder, and in this case the latter functions as an additional respiratory organ. In this case, the swim bladder is connected to the intestine by a wide and short channel directly behind the pharynx. The entrance is supplied with its own musculature and sometimes resembles the glottis, especially if it lies on the ventral side of the intestine, as in lungfish and the African bichir (Polypterus). The surface of such an organ is increased by the formation of numerous inward projections, so that the walls of the bladder acquire a honeycomb character, quite resembling the walls of the lungs in amphibians. The similarity with the lungs is further increased in this case because in bichirs and also in some lungfish, this organ is paired, supplied with blood through the pulmonary artery, which branches off from the fourth pair of gill arteries (as in terrestrial vertebrates), and carries the oxidized blood through the pulmonary vein directly into the venous sinus of the heart. It should be recognized that the lungs of vertebrates, in their origin, represent such an additional respiratory organ that developed as a paired outgrowth in the posterior part of the gill region of the intestine. With the transition to life on land, the gills were reduced, and the lungs remained as the only organ of aerial respiration. In amphibians, these are still very imperfect organs and are very often supplemented by other respiratory organs—often aquatic (external gills), but sometimes also aerial. Thus, in most amphibians, the skin itself is an important respiratory organ and is abundantly supplied with venous blood from the cutaneous branch of the pulmonary artery. In other amphibians, the mucous membrane of the oral cavity also plays such a role, the surface of which can be increased by the formation of numerous folds. In some amphibians, the lungs even become completely reduced, being replaced by these additional organs. In amphibians, the lungs are laid down as a paired outgrowth of the intestinal wall, directly behind its gill region. As they further develop in the form of elongated tubes that then form lung sacs, the connecting ventral part of the intestinal tube separates into a small unpaired chamber. In tailless amphibians, even in the adult state, the lungs are connected only by a small laryngo-tracheal chamber, opening into the pharynx by the glottis. In tailed amphibians, in connection with the formation of the neck, this chamber elongates into a more extensive tube, sometimes already dividing at the end into two small bronchi. In higher vertebrates, the respiratory pathways leading air to the terminal point—the pulmonary alveoli—become increasingly important, and first of all, the unpaired parts—the larynx and trachea—develop very significantly. The increase in the respiratory surface of the lung sacs in amphibians begins with the formation of numerous inward projections dividing their peripheral part into numerous cells. On the walls of the larger cells, secondary projections and a system of smaller secondary cells develop. In reptiles, the process goes further—the projections grow, and the walls of the sacs acquire a completely spongy character. The larger projections deeply indent into the interior of the lung cavity, leaving in higher forms only a relatively narrow central passage free. The edges of the septa grow and are covered with ciliated cylindrical epithelium. The central passage takes on the role of a respiratory pathway, being the intrapulmonary continuation of the main bronchus. From the central passage, openings between the septa lead into the peripheral cellular chambers, inside of which the same process continues further. Here their own central passages arise, cylindrical epithelium develops along the inner edges of the septa, and thus intrapulmonary bronchi of the second order, then of the third order, etc., are formed. The cartilaginous skeleton, which first appears in the larynx, then spreads in the form of cartilages and half-rings along the trachea, extends to the main, and sometimes to the secondary bronchi. Among reptiles, crocodiles and turtles have the most perfect lungs. In birds, the development of intrapulmonary air passages reaches its highest limit, but at the same time it is very peculiar. The enlarged main bronchus leads into 4-6 ventral and a larger number of dorsal secondary bronchi. From the latter, numerous parallel tertiary bronchi, so-called parabronchi, branch off. From the parabronchi, numerous branched small bronchioles with cellular walls branch off. The parabronchi are connected to each other by numerous anastomoses, so they form a very complex network of interconnected air passages. In addition, another important feature is the so-called air sacs. The latter are very thin-walled extrapulmonary continuations of the main bronchus and the four secondary bronchi. These air sacs are partly located in the abdominal cavity between the internal organs, partly grow beyond it—between the muscles and finally inside the bones (pneumatization of bones). The following main sacs are distinguished: paired cervical, anterior thoracic, posterior thoracic, abdominal and unpaired interclavicular. The significance of the air sacs of birds lies not only in reducing the specific gravity of birds—they also play a major role in respiration, functioning as bellows that draw air through the lungs. The lungs themselves in birds are little distensible, and during respiratory movements of the chest, only the air sacs stretch and compress. During flight, there are no actual respiratory movements, and respiration occurs passively due to the periodic compression of the axillary and thoracic sacs with each downstroke of the wing. This unique respiratory system results in the residual air in birds being mainly confined to the air sacs, while the lungs themselves are ventilated more completely than in other vertebrates.

The lungs of mammals are more complex compared to the lungs of reptiles only in the sense of a significant complication of the bronchial branching system. In addition, the bronchi and their smaller branches are much more isolated from the lung tissue itself. While in reptiles there are openings everywhere in the bronchi leading to the alveolar tissue, in mammals only the final branches—the bronchioles—end in dilations—funnels with mesh-like walls. As a result of the gradual complication of lung structure, in the series of vertebrates, the respiratory pathways leading to the actual respiratory surface become increasingly isolated, and at the same time their total length increases significantly. On the other hand, the respiratory surface increases considerably due to the significant increase in the total number of pulmonary alveoli. The mechanism of respiration varies in different vertebrates. Amphibians pump air from the oral cavity through the glottis into the lungs with the mouth and nasal valves closed by contracting the muscles of the floor of the mouth. Other vertebrates draw air into the lungs by expanding the thoracic region, which is achieved by raising the ribs. The mechanism of respiration is most perfect on the one hand in birds, and on the other—in mammals; in the latter the thoracic cavity is isolated from the abdominal one, and a special respiratory muscle—the diaphragm—develops in the diaphragm. Respiratory pathways. In tailless amphibians, as mentioned, the lung sacs communicate with the glottis through only a very small chamber. In tailed amphibians, this chamber elongates into a tube and differentiates into 2 parts—the anterior part with muscles and cartilages supporting the glottis, and the posterior part—the trachea. Starting from reptiles, the posterior end of the trachea divides into two bronchi, corresponding to both lung sacs. In amphibians, the larynx is supported by one or two pairs of cartilages, of which the posterior pair in tailless forms forms one ring-shaped cartilage, and the anterior—arytenoid cartilages—supports the vocal cords. The same cartilages are also found in reptiles and birds. In the latter, the larynx is not a vocal organ—such develops in them at the place where the trachea divides into both bronchi (the "lower larynx"). In mammals, the larynx is constructed much more complexly. In addition to the arytenoid and cricoid cartilages, which correspond to the cartilages of the same name in lower forms, there is also the thyroid cartilage and the epiglottis sitting on it in front. The mammalian larynx is closely connected with the hyoid apparatus and clearly shows its origin from parts of the gill skeleton—especially the thyroid cartilage, developing from the II and III gill arches of the embryo. The cartilages of the trachea also show a certain connection with the laryngeal cartilages during their formation, which in tailed amphibians are represented by small, unevenly scattered cartilages, while in reptiles they form regular semicircles or even complete rings. In birds, the latter often ossify, the trachea itself reaches considerable length, forms bends that sometimes go inside the keel of the sternum, and serves as a resonator. In mammals, resonators are often paired or unpaired sac-like outgrowths in the laryngeal area.

I. Shmal'gauzea. Pathological Physiology of the Respiratory Organs. The main function of the lung is the introduction into the organism and removal from it of gaseous substances. The methodology of research in this area is still insufficiently developed to this day, and our knowledge here is currently concentrated mainly on the elementary exchange of oxygen and carbon dioxide. A decrease in normal gas exchange is observed when the respiratory surface of the lung is reduced due to the filling of the alveoli with inflammatory or serous exudate (inflammation and edema of the lung), when their lumen is narrowed by dilated vessels in case of blood stasis (heart diseases); when they are compressed by proliferating and scar connective tissue (tuberculosis, syphilis of the lung), in atrophy of the alveoli (emphysema), when the lung is compressed by pleural exudate, tumors, when the diaphragm is high in connection with diseases of abdominal organs; when there is difficulty in the patency of the air passages, especially the small bronchi due to inflammatory processes in them (capillary bronchitis) or spasm of their muscular wall (bronchial asthma); finally due to disruption of the mechanism of respiratory movements in diseases of the chest wall. Lack of oxygen, especially excess of carbon dioxide in arterial blood irritates the respiratory center of the medulla oblongata and to a certain degree is easily compensated by changes in the depth and rhythm of respiratory movements, but mainly by strengthening the pulmonary circulation by increasing the volume and frequency of heart contractions. However, this compensation is possible only up to certain limits, beyond which disruption of gas exchange causes a sensation of lack of air and actively intensified, tense breathing - shortness of breath (see), which manifests itself in all circumstances accompanied by significant intensification of the general metabolism in the body and disturbances in vegetative innervation: during physical work, infections, auto-intoxications, mental excitations. The shortness of breath observed in diseases of the R. o. depends to a large extent on insufficiency of pulmonary circulation, since a gradual decrease in respiratory surface even by half, e.g. in artificial pneumothorax, does not lead to shortness of breath if the heart is sufficiently efficient. However, slowing of pulmonary circulation in heart diseases is usually accompanied by shortness of breath with completely normal lungs. Insufficient arterialization of blood, not sharply expressed and prolonged, can also be compensated by an increase in the number of erythrocytes and an increase in hemoglobin (in the climate of high mountains, partly in chronic interstitial processes in the lungs). The respiratory function of the lungs, ensuring external gas exchange - between the blood and the external air, is regulated by internal gas exchange - between the blood and the tissues, where complex biochemical processes occur with absorption of oxygen and release of carbon dioxide (see also Tissue respiration). Tissue respiration is the primary stimulus for the work of the lungs through the medium of blood and the respiratory center. Therefore, changes in lung function are observed in anomalies of blood (e.g. after significant blood loss, in anemias with a sharp decrease in hemoglobin content), also in violations of tissue metabolism and in diseases of organs leading to enhanced formation and excessive content in the blood of not fully oxidized metabolic products (lactic acid, amino acids, uric acid, β-oxymethylacetic acid), in various infections and intoxications. Disorders of the functions of endocrine glands, disruption of the work of the central vegetative nervous system from various causes, including from mental influences, can sharply change the chemical processes in tissues and thereby affect the respiratory exchange of the lungs. Thus, the respiratory function of the lungs is in close connection and even dependence on many other organs and systems. Disorders in the activity of each member of this chain can lead to disruption of lung function, and conversely - diseases of the lungs often lead to disorders of other organs and the whole organism. Diseases of all organs have a close mutual connection. It has not yet been finally clarified whether gas exchange in the lung occurs exclusively according to the physical laws of partial pressure of gases without the active participation of the lung epithelium in this (Bohr, Krogh) or whether the living partition between the air of the alveoli and the blood flowing in the vessels has partly a secretory gas function (Haldane). In the latter case, gas exchange in the lung must also depend on the functional state of the lung epithelium and must be even more closely connected with the nutrition, innervation and other conditions of life of the lung tissue itself. In addition to the above-mentioned role of the lung in gas exchange, the lung itself directly participates in the general metabolism, for example in the chemical processes of transformation of fats circulating in the blood vessels of its lungs (Roger, Büttner'); this function of the lung (lipolysis) has not yet been studied in detail, but it undoubtedly must also be disrupted in diseases of the lung, and may be in connection with this stands the tendency to weight loss in chronic lung patients. The bronchial system has first of all purely mechanical significance: it is a drainage network for ventilation of the pulmonary alveoli. Difficulties for air circulation in its small branches occur with inflammatory swelling of the bronchial mucous membrane, and accumulation of mucus at this time can completely block their lumen. In widespread capillary bronchitis in children, severe disorders of gas exchange appear; with compression of large bronchi by tumors, enlarged lymphatic glands, with blood flowing into the bronchi from ruptured vessels, access of air can completely cease even into an entire lobe of the lung - it is excluded from gas exchange, collapses (atelectasis). Then inflammatory processes can develop here. In bronchial asthma, under the influence of innervation disorders, convulsive contractions of the muscular wall of the bronchi and enhanced secretion of mucus occur, leading to significant disorders of the respiratory act. In inflammatory processes in the bronchi, the sensitivity of their mucous membrane to irritations from air and from accumulating mucus and inflammatory products in the bronchi increases. This causes by reflex a special modification of respiratory movements - cough (see). Prolonged, sharp cough excessively stretches the pulmonary alveoli with their vessels, hinders circulation and gas exchange, promotes during the inhalation phase the aspiration of mucus and products of inflammation and disintegration into deeper parts of the lung. Chronic cough promotes the development of emphysema. Sharp fluctuations in intrathoracic pressure during cough can disrupt the activity of the heart and thereby further disrupt gas exchange in lung patients, often cyanotic for this reason. The walls of the bronchi have other functions, extremely important for the self-protection of the lung from harmful external influences and for self-cleansing of the organ from contaminants penetrating into it from outside or forming in it itself. Thanks to the abundance of lymphatic vessels, the bronchial walls have the ability to absorb fluids. Bleeding into the lumen of the bronchi is very quickly resorbed if the blood has not yet clotted; the same is observed with artificial introduction of sprayed liquids with medications (inhalation). Semi-liquid and even dense inflammatory exudates in the bronchi and alveoli are also resorbed, undergoing preliminary enzymatic liquefaction - in lobar pneumonia, sputum may be completely absent, and the entire exudate is resorbed in place. Air passing through the bronchi is warmed, moistened, cleansed of mechanical impurities, which settle on the mucus-covered walls of the bronchi and then are removed back by the movements of the ciliated epithelium, not reaching the alveoli. This process begins already in the upper respiratory tract. However, when inhaling a large amount of dust, these measures prove insufficient. Then bronchial catarrhs develop. In the depth of the lung in the area of the alveoli, vascular capillaries are abundantly developed and a rich network of lymphatic vessels is laid, in which accumulations of lymphoid elements are located, reaching considerable sizes in places, and at the branching points of the bronchi there are already fully organized lymphatic glands, increasing as the diameter of the bronchi increases and reaching maximum development at the bifurcation of the trachea in the so-called gates of the lung (hilus). Lymphatic pathways and intercellular lymphatic slits abound with cells capable of phagocytosis. Even the endothelium of the pulmonary capillaries has the ability to phagocytose. Dust particles entering during inhalation are phagocytosed by leukocytes wandering in the superficial layers of the bronchial mucous membrane and so-called dust cells in the alveoli and are carried along the lymphatic pathways to the nearest lymphatic glands, where they are deposited. In excess, dust particles are transferred to further glands up to the glands of the lung gates and can even penetrate through them and through the thoracic duct enter the general circulation and be deposited in other organs, e.g. in the liver.

In newborns, the lung has a pink color, but with age it gradually becomes filled with dust and takes on a gray color, while in the lung glands an almost black coloration is observed. In dusty occupations, the entire lung takes on a color corresponding to the nature of the inhaled dust. The dust deposited in tissues can have a chemically irritating effect. Around accumulations of foreign particles in the lymphatic pathways, around small bronchi, chronic inflammatory processes develop with an outcome in fibrosis in the form of separate scattered foci or strands in the lung or in the form of a diffuse interstitial process (see Pneumoconioses). These processes are often accompanied by emphysema, disorders of pulmonary circulation. Of particular importance is the contamination of the lung by microbes. Penetrating into the air passages together with the inhaled air, microbes usually settle already in the first branches of the large bronchi on their moist walls. From here they are removed by the movements of the ciliated epithelium or are phagocytosed and digested by wandering cells. The mucus of the bronchi itself can dissolve microbes (bacteriolysis); even the most resistant of them - tubercle bacilli - are dissolved in sputum when it is kept in an incubator (for this reason, bacilli are often absent in the mucus on the walls of old tuberculous cavities). Under normal conditions, lung tissue is sterile; lung infarcts are usually not accompanied by suppuration. Even by inhaling sprayed cultures in healthy animals, it is difficult to obtain lung infection with the integrity of the bronchial mucosa; however, infection is easily achieved with preliminary damage to the mucosa, e.g., by chemical irritants. But still many pathogenic microbes do not perish during phagocytosis, especially in weakened organisms, in which the enzymatic activity in cells and fluids is reduced, or in massive virulent infections even in healthy subjects or when infected with very resistant microbes, such as the tubercle bacillus. Then inflammatory processes arise, which can also be considered as an act of self-defense (see Inflammation), but this does not always give quick and positive results. Thus, infectious bronchitis, pneumonia arise. Carried by phagocytes into the depths of the tissues, microbes are carried by the lymph current into the lymph glands, causing inflammatory processes there, acute or chronic; from here infection can spread further by the lymphogenous path to the hilar lymph glands and even pass through them and give hematogenous dissemination in other organs or general septic disease. In the development of infectious inflammatory processes in the lungs, the sensitization of the organ and the body by previous infections plays a role, which leads either to increased anaphylactic-type sensitivity and gives rapidly developing extensive lesions (pneumonia cruposa lobaris, infiltrates during exacerbations of old tuberculous foci) or conversely - is accompanied by a decrease in reaction and the development of immunity. Chronic infectious processes in the lung usually develop in the interstitial connective tissue in the form of infiltrates, peribronchitis, perivasculitis; they have the so-called productive character, accompanied by abundant development of connective tissue in the form of separate foci, strands or diffuse growths. But they can also acquire the character of chronic pneumonias, which can also end with the organization of fibrosis or undergo necrosis, disintegration with the formation of cavities. The latter occurs even more easily in acute infectious inflammations (abscesses, gangrene). With the spread of infectious processes in the lung, the pleura is usually also involved. Infectious diseases of the lungs, in addition to local pulmonary symptoms and in addition to the usual influence on other organs in all pulmonary ailments (see above), also give phenomena of general infectious intoxication, and sometimes hematogenous metastases of infection to other organs. - Besides the penetration of microbes with the inhaled air (aerogenously), infection can be carried into the lungs from other organs through the blood, e.g., lung abscesses in septic diseases, pneumonia and bronchitis in general infections. It has been experimentally proven that microbes introduced directly into the blood and circulating in the pulmonary vessels are phagocytosed by the cells of the endothelium of the pulmonary vessels, are carried into their outer layers and perivascular spaces. Injuries to the lung can also be the cause of inflammatory processes. All functions are performed correctly with the normal general state of the organism, and all its adaptations of self-defense prove to be sufficient only for the usual external conditions of life, to which the organism can adapt. But everything that suppresses the elementary life processes, that weakens the organism as a whole and reduces its resistance to harmful external influences, all sharp fluctuations of factors of the external environment, all this contributes to the disturbance of pulmonary functions and the development of pathological processes in the lung. This includes above all various diseases of other organs, especially of the cardiovascular system and the so-called general diseases. But no less important are insufficient nutrition, depressing influences of the external environment: bad general sanitary-hygienic and social conditions, various professional harmfulness, especially the so-called dusty occupations or occupations associated with the inhalation of irritating gases, with significant fluctuations in temperature and humidity of the air, individual sharp coolings of the body, intoxications (alcoholism), all kinds of overwork, heavy mental experiences (through the vegetative centers). However, not all people are equally susceptible to various harmful factors. In this respect there are large differences, which are determined by individual characteristics - congenital, constitutional or acquired in previous life under certain conditions of the external environment. For the same reason, pulmonary diseases similar in pathogenesis and anatomical form develop and proceed differently in different people. Thus e.g. in childhood and youth there is more tendency to acute than to chronic pulmonary processes; the latter develop more easily in old people; tuberculous pulmonary processes in the picnic constitution give more acute forms than in asthenics. General hygienic and social factors have enormous importance both in the pathogenesis of pulmonary diseases and in their prevention. On the pathology of D. o. see also articles on individual organs (Bronchi, Larynx, Lungs, Trachea) and on individual diseases (Bronchitis, Pneumonia, etc.). i. vorobyev. Statistics of diseases of the respiratory organs. In 'diseases of the respiratory organs', according to the new nomenclature of diseases and causes of death, are included: 1) diseases of the nasal cavity and its appendages, 2) diseases of the larynx, 3) inflammation of the bronchi, 4) bronchopneumonia, 5) inflammation of the lung (pneumonia), 6) inflammation of the pleura (pleurisy) and pneumothorax, 7) hyperemia and parenchymatous hemorrhage of the lung, 8) gangrene of the lung, 9) bronchial asthma, 10) emphysema of the lungs and 11) other diseases of the respiratory organs (except tuberculosis). This also includes lobar pneumonia, which according to the old nomenclature was classified as 'contagious diseases'. Mortality. The number of dying from diseases of the respiratory organs in individual countries annually amounts to about 15% in relation to total mortality. In northern countries (Sweden, Norway) this percentage is lower than in Central European and especially in southern countries (e.g. in Italy). Table 1 shows mortality rates from diseases of the respiratory organs per 100 deaths from all causes in some countries for 1921-23. Table 1. Number of deaths from diseases of the respiratory organs per 100 deaths from all causes. Countries 1921 1922 1923; England . . Belgium . . Germany . Holland . Denmark . . Spain . . Italy . . Norway . Scotland Sweden . . 16.4 14.2 13.0 14.4 14.4 15.6 16.8 10.7 14.6 10.5 18.0 16.7 13.9 16.7 15.3 16.8 19.1 11.8 17.5 11.2 16Д 13.2 12.3 13.2 16.6 17.3 13.4 Per 100,000 inhabitants annually in individual European countries from 120 to 300-400 people die from diseases of the respiratory organs. Of European countries, the lowest mortality rates from diseases of the respiratory organs in relation to the population are observed in Sweden and Norway, the highest - in Spain and Italy. The presence of certain epidemics significantly increases this figure. Especially sharply affects the increase in registration of mortality from diseases of the respiratory organs influenza (see). Table 2 shows mortality rates from diseases of the respiratory organs in individual European countries per 100,000 population for the period from 1911 to 1925. The influenza pandemic of 1918 (the so-called 'Spanish flu') gave a sharp increase in mortality from diseases of the respiratory organs in all countries listed in the table, and in some it increased almost 1½-2 times compared to 1917. An increase in mortality from diseases of the respiratory organs is also noted in 1922, in connection with a new increase in influenza. For all years listed in the table, Sweden and Norway give the lowest mortality rates from diseases of the respiratory organs, Spain and Italy - the highest. The group 'diseases of the respiratory organs' also includes mortality from inflammation of the lungs, which in individual countries ranges from 20% to 50% and more in relation to the total mortality of this group (in Denmark and Spain - somewhat lower - about 15%).

Table 3 shows the number of deaths from diseases of the respiratory organs in 1922. Table 2. Number of deaths from diseases of the respiratory organs per 100,000 inhabitants. Years k v k V < 5 V o i k v y V o v a n i p s. o ! e v y a v - 1924; .... 221 218 199 197 210 211 241 345 214 193 179 198 171 143 138 216 190 181 208 205 193 322 235 181 161 191 131 126 126| 332 348 378 403 371 648 367 328 293 338 287 - 148 251 140! 292 154^! 261 161! 249 142| 275 266! 351 1671 274 - - - - 262 238 244 318 228 233 433 375 252 201 261 185 Table 3. Number of deaths from individual forms of diseases of the respiratory organs in 1922 (absolute numbers). Countries Bronchitis England . . Hungary . Holland . Denmark . . Spain . Italy . . Scotland Pneumonia Other diseases of resp. organs Total 88.044 22.362 13.446 6.058 74.038 126.422 12.7S0 Large fluctuations in the relationships between mortality from individual forms of diseases of the respiratory organs in different countries (e.g. between 'bronchitis' and 'pneumonia' in England and Holland or Spain and Italy) are probably explained by the different approaches of doctors from different countries to post-mortem diagnosis. The group 'bronchitis' includes acute and chronic bronchitis. The main mass in all countries consists of mortality from 'bronchitis' in children under 5 years of age. Tuberculosis, as already mentioned, according to international nomenclature, is not included in 'diseases of the respiratory organs'. For more details on mortality from pneumonia - see Pneumonia. Mortality by age is illustrated by data from Germany for 1912-13 and 1925-26 (Table 4). All cases of death from diseases of the respiratory organs were included in the statistics, with the exception of pneumonia. Table 4. Mortality from diseases of the respiratory organs by age groups in Germany (per 100,000 persons of the corresponding group). Age 1912 1913 1925 1926 0- 1 year....... 1-15 years....... 15-30 years ...... 30-60 years ...... 60-70 years ....... 70 years and older . . . On average . . . The highest mortality is noted in early childhood and old age. 1925-26 compared to 1912-13 showed a decrease in mortality in all age groups (except for the age from 1 year to 15 years). In early childhood and old age, mortality among men is higher than among women. For example, the corresponding mortality in Germany for 1925 and 1926 is given (Table 5). Table 5. Mortality from diseases of the respiratory organs by sex and age in Germany (per 100,000 persons of the corresponding group). 1925 1926 ! Age m. f. m. 0- 1 year....... 1-15 years....... 15-30 years ...... 30-60 years ...... 60-70 years ...... 1 70 years and older . . , 197 485 140 358 461 35 6 28 196 520 For the USSR (Russia), there are materials on mortality from diseases of the respiratory organs in the cities of the European part of the Union (Russia), where it amounts (together with pneumonia) to about 15% in relation to total mortality; in particular, in Moscow and Leningrad it varies in some years from 15% to 17.5%. Mortality per 100,000 population from diseases of the respiratory organs is given in Table 6. Table 6. Number of deaths from diseases of the respiratory organs per 100,000 inhabitants in Moscow and Leningrad. Years Moscow Leningrad 468 479 331 323 336 194 366 325 267 222 273 177 In Odessa for the same years, mortality from diseases of the respiratory organs ranged from 150 to 200 per 100,000 population, i.e. less than in Moscow and Leningrad. In 1926, mortality from diseases of the respiratory organs is recorded significantly lower than in the pre-war period. Table 7 shows mortality from diseases of the respiratory organs by age groups for 1926 in Moscow and Leningrad. About half of the deaths from diseases of the respiratory organs occur in children under 1 year of age and about 25% in the age group from 1 year to 4 years. Morbidity. According to reports on the state of public health of the Chief Medical Inspectorate, annually about 10 million cases of diseases of the respiratory organs were registered on an outpatient basis in Russia. This group included: inflammation of the respiratory tract, catarrhal pneumonia, inflammation of the costal pleura and other diseases of this group (pneumonia was not included). The ratio of individual forms of this group is seen in Table 8 (absolute numbers). Table 7. Number of deaths from diseases of the respiratory organs by age groups in Moscow and Leningrad in 1926 (per 100 deaths from this group of diseases in all ages). Age Moscow Leningrad 0- 1 year.......... 1- 4 years.'......' . . . 46,1 27,9 0,8 0,7 0,8 1,1 1,3 3,4 4,3 5,3 4,7 3,6 48,0 21,4 1,8 0,4 0,7 1,+ 1,2 3,7 5,1 6,3 6,5 4,0 5- 9 years......... 10-14 years ......... 15-19 years......... 20-24 years......... 25-29 years..... 30-39 years......... 50-59 years ......... 60-69 years ........ 100,0 100,0 Table 8. Diseases 1912 1913 1914 Inflammation of resp. tract . . . Catarrhal pneumonia . . Inflammation of costal pleura . . . Other diseases of this group ..... 7.968.647 894.519 622.622 7.787.200 861.322 634.355 7.709.677 791.503 560.173 Total .... Diseases of the respiratory organs (without pneumonia) constituted about 10% among all outpatients and about 5% among inpatients of all patients under treatment in hospitals. Morbidity from diseases of the respiratory organs for 1902-14 in relation to the total number of outpatient and inpatients is seen in Table 9. Table 9. Morbidity from diseases of the respiratory organs in relation to the total number of outpatient and inpatients. Years % to total number of patients outpatient inpatient 1902-05........ 1906-10......... 10,9 11,0 10,9 11,4 10,7 11,2 5,4 5,0 5,0 5,1 5,0 5,1 As can be seen from the table, this percentage remains stable and in individual years shows very small fluctuations. According to zemstvo studies, diseases of the respiratory organs (without pneumonia) constituted in individual provinces from 7.0% to 10% of all outpatients (Table 10). In 1926, diseases of the respiratory organs (including pneumonia) constituted in the Moscow Province 10.1% in relation to the sum of all diseases and 112.8 per 1,000 population, in the city of Moscow - 8.0% to the sum of patients and 106.1 per 1,000 population. Morbidity by sex is illustrated by the following data for the Moscow Province for 1926 (rates per 1,000 population; Table 11). Table 10. Provinces Years % to sum of patients Yekaterinoslavskaya . . . 1898-1902 1898 1891-1895 1898-1902 1903 1838-1900 1887-1892 8,7 9,4 10,2 10,8 10.2 7,1 6,8 8.7 9,9 and the city of Moscow for 1926 (rates per 1,000 population; Table 11). Table 11. Moscow Province Moscow...... Men 124,6 119,7 Women 102,4 93,2 Both sexes 112,8 103,1 Table 12. Morbidity from diseases of the respiratory organs by age groups and sex in the Moscow Province and the city of Moscow for 1926 (per 1,000 pop). Age Under 1 1- 4 5- 9 10-14 15-19 20-29 30-39 40-49 50-59 60 years and older Moscow prov. city Moscow m. f. 201,5 191,3 m. f. 294,8 248,3 136,7 136,3 186,2 177,7 65,0 74, B 113,7 113,1 80,0 91,3 97,9 117,5 120,3 102,1 111,0 92,8 151,1 103,9 118,8 82,6 127,2 103,5 105,6 78,2 123,7 97,7 108,1 74,1 120,9 87,9 Я6,9 58,1 81,4 57,3 74,1 43,6 Among men, diseases of the respiratory organs are registered more often than among women. Morbidity by age and sex in the Moscow Province and the city of Moscow for 1926 is given in Table 12 (see also Fig. 1). The highest morbidity from diseases of the respiratory organs, both in the Moscow Province and in the city of Moscow, is noted in infancy and in the age group from 1 year to 4 years; the next maximum falls on the age from 20 years to 29 years (for women in the city of Moscow - from 10 years to 14 years). Men show higher morbidity than women in the age up to 4 years and over 15 years; from 5 years to 14 years among women, diseases of the respiratory organs are registered more often than among 160 150 140 130 120 110 100 90 80 70 60 | 163 g \ 1l\*-^ docKOa.ryf . Moscow t^' 129' Ji Ч" ^ч~ ^-K 01- ч \ / V. Ч / /- 10 0 Table 13. Age Under 1 year 1- 4 years 5- 9 years 10-14 years 15-19 years 20-29 years 30-39 years 40-49 years 50-59 years 60 years and older Morbidity by sex in M Acute bronchitis Figure 1. Morbidity of respiratory organs by age and sex in the Moscow Province for 1926 "(per 1,000 pop. of corresponding group). men. Morbidity by individual forms of diseases of the respiratory organs by age and sex is presented in Tables 13 and 14 (rates per 1,000 population of corresponding group). p- by age [osity by individual forms of diseases of the respiratory organs in the Moscow Province for 1928 (per 1,000 pop. of corresponding group) 185,4 88,8 16.9 16.2 21,6 25,4 19,3 18,7 16,7 10,3 Chronic bronchitis Pneumonia 177,7 92.0 19,1 16,7 13,0 14,6 14,5 14,9 13,9 8,3 3,4 3,4 26,0 33,0 51.1 69,3 58,0 58,4 54,0 38,4 10,4 3,0 2,0 2Д 1,8 1,9 2,5 2,7 2,3 1,3 1,8 2,3 1,5 Chronic rhinitis Laryngo-tracheitis Bronchial asthma Pleuritis m. f. m. f. m. f. m. f. Emphysema 8,5 8,0 9,5 8,5 1,0 0,7 5,4 5,6 7,1 6,4 -- 1,1 0,8 - 5,2 7,2 4,5 4,8 - 1,5 1,7 - 9,2 15,5 9,6 10,6 0,1 0,1 2,8 3,2 - 11,6 21,3 14,3 19,2 0,1 0,1 8,3 5,4 0,1 8,7 10,8 15,9 19,8 0,2 0,2 14,8 9,7 0,4 4 R 6,5 11,8 18,0 0,4 0,3 16,3 11,8 1,9 3 2 5,4 9,8 13,8 0,4 0,4 15,6 10,7 7,2 2,4 3,5 7,3 8,0 0,5 0,4 1,3 7,8 14,8 1,0 1,6 2,8 3,3 0,4 0,3 6,2 3,2 13,1 0,1 0,1 0,3 0,3 1,2 2,8 4,2 Table 14. Morbidity by individual forms of diseases of the respiratory organs by age and sex in the city of Moscow for 1926 (per 1,000 pop. of corresponding group). Age Acute bronchitis Under 1 year 1- 4 years 5- 9 years 10-14 years 15-19 years 20-29 years 80-39 years 40-49 years 50-59 years 60 years."

Table 7. Morbidity from diseases of the respiratory organs (per 1,000 population) by age and sex in 1926 (Moscow province and city of Moscow):

Age (years) | Men | Women --- | --- | --- 0-1 | 121.6 | 106.9 1-4 | 32.1 | 16.8 5-9 | 19.8 | 21.9 10-14 | 20.2 | 20.7 15-19 | 17.8 | 10.5 20-29 | 117.0 | 103.6 30-39 | 33.4 | 8.8 40-49 | 11.0 | 12.4 50-59 | 12.9 | 8.8 60+ | 6.6 | 6.6

Chronic bronchitis: Age (years) | Men | Women --- | --- | --- 0-1 | 2.6 | 3.8 1-4 | 23.9 | 15.9 5-9 | 22.0 | 30.2 10-14 | 29.2 | 31.9 15-19 | 29.0 | 21.5 20-29 | 2.0 | 3.5 30-39 | 23.8 | 16.8 40-49 | 10.0 | 13.6 50-59 | 15.1 | 17.0 60+ | 17.2 | 15.4

Croupous pneumonia: Age (years) | Men | Women --- | --- | --- 0-1 | 4.8 | 5.1 1-4 | 4.5 | 4.0 5-9 | 1.9 | 1.8 10-14 | 1.1 | 0.8 15-19 | 1.6 | 0.6 20-29 | 0.9 | 0.6 30-39 | 1.0 | 0.6 40-49 | 1.7 | 1.7³ 50-59 | 1.5 | 1.4 60+ | 2.0 | 1.3

Chronic rhinitis: Age (years) | Men | Women --- | --- | --- 0-1 | 14.3 | 17.9 1-4 | 25.4 | 31.6 5-9 | 23.0 | 17.7 10-14 | 10.0 | 7.6 15-19 | 5.3 | 4.0 20-29 | 18.3 | 19.2 30-39 | 0.2 | 0.2 40-49 | 2.0 | 12.2 50-59 | 0.1 | 0.1 60+ | 2.1 | 15.9

Laryngotracheitis: Age (years) | Men | Women --- | --- | --- 0-1 | 17.0 | 0.3 1-4 | 0.2 | 0.2 5-9 | - | 0.3 10-14 | - | 1.5 15-19 | 0.3 | 5.3 20-29 | 0.6 | 11.6 30-39 | 2.1 | 13.2 40-49 | 31 | 0.2 50-59 | 0.2 | 0.2 60+ | 4.8 | 0.5

Bronchial asthma: Age (years) | Men | Women --- | --- | --- 0-1 | 18.8 | 0.4 1-4 | 19.0 | 0.6 5-9 | 0.5 | 7.7 10-14 | 16.7 | 0.8 15-19 | 17.1 | 0.6 20-29 | 9.3 | 9.3 30-39 | 15.2 | 1.0 40-49 | 13.6 | 1.2 50-59 | 10.5 | 1.2 60+ | 6.9 | 1.2

Pleurisy: Age (years) | Men | Women --- | --- | --- 0-1 | 8.0 | 1.2 1-4 | 5.9 | 1.2 5-9 | 2.4 | 0.9 10-14 | 1.2 | 6.4 15-19 | 1.0 | 1.0 20-29 | 1.5 | 1.5⁹ 30-39 | 3.0 | 3.0 40-49 | 3.6 | 6.0 50-59 | 6.7 | 6.7 60+ | 5.1 | 3.0

Emphysema: Age (years) | Men | Women --- | --- | --- 0-1 | 0.2 | 0.2 1-4 | - | - 5-9 | 0.3 | - 10-14 | - | 1.5 15-19 | 0.3 | 0.3 20-29 | 5.3 | 0.6 30-39 | 11.6 | 2.1 40-49 | 13.2 | «31

Acute bronchitis shows the highest morbidity in infancy and somewhat less in the age group from 1 year to 4 years. In the following age groups, morbidity from it sharply decreases and remains at approximately the same level (with some increase observed in the age group from 20 to 29 years) until old age, when morbidity from acute bronchitis significantly decreases. Among the male population under 1 year of age and 15 years and older, acute bronchitis is recorded more frequently than among females (in the city of Moscow also in the age group from 1 year to 4 years). Chronic bronchitis, on the contrary, is very rarely recorded before the age of 5 years, after which it sharply rises and remains at high figures in all subsequent ages. Starting from 15 years, it is recorded more frequently among men than among women. Croupous pneumonia is most often observed before the age of 5 years, with some increase noted in old and senile ages. Among men, croupous pneumonia is recorded more frequently than among women in all age groups. Chronic rhinitis is more frequently recorded in childhood and young ages; after the age of 30 years, it is noted significantly less frequently. In most age groups, chronic rhinitis is recorded more frequently among women than among men. Laryngotracheitis changes little with age, and only in old age is a noticeable decrease in diseases observed. Bronchial asthma is observed mainly after the age of 30-40 years, approximately equally among men and women. Pleurisy is concentrated mainly in working age from 20 to 49 years (in the city of Moscow - up to 59 years) and is generally observed more frequently among men than among women. Emphysema of the lungs is a disease of old and senile ages; among men, it is observed significantly more frequently than among women.

Seasonality of morbidity from diseases of the respiratory organs. Table 15 (and in Fig. 2) presents data on the monthly incidence of diseases of the respiratory organs in the Moscow province and city of Moscow for 1926 (average monthly morbidity is taken as 100). Table 15. Months

Months | City of Moscow --- | --- January | 102 February | 146 March | 129 April | 122 May | 95 June | 77 July | 67 August | 67 September | 65 October | 77 November | 82 December | 91

The maximum incidence of diseases of the respiratory organs in the Moscow province occurs in March, the minimum - in August-September; in the city of Moscow - the maximum is in February, the minimum - in July-August. For individual forms of this group, the maximum incidence in 1926 occurs: in the Moscow province - acute bronchitis, chronic bronchitis, croupous pneumonia, laryngotracheitis - in March, chronic rhinitis, bronchial asthma and emphysema of the lungs - in February; in the city of Moscow - acute bronchitis, chronic rhinitis and pleurisy - in March, chronic bronchitis, laryngotracheitis - in February, croupous pneumonia - in April, bronchial asthma - in February and April, emphysema of the lungs - in January and April.

Diseases of the respiratory organs and profession. The question of the relationship between diseases of the respiratory organs and profession was approached by our zemstvo statisticians. Thus, A. I. Shingarev, based on the processing of materials from the Voronezh province for 1898-1902, provides the following indicators of morbidity from diseases of the respiratory organs (in % of the total for each group): among peasant farmers - 8.5, among factory workers - 8.4, rural workers - 8.3, artisans - 9.5, domestic servants - 8.9, intellectual professions - 11.9, traders - 9.4. More definitive conclusions are obtained by P. I. Kurkin. Based on materials from the Moscow province for 1898-1902, he establishes the following indicators of morbidity from diseases of the olfactory and respiratory organs among various groups of patients (per 1,000 of all patients): among the rural population - 97.2, urban - 123.6, factory - 129.4, i.e., among the factory population, these diseases are observed significantly more frequently than among the urban population, and especially - rural. In particular, acute bronchitis among the rural population during this period amounted to 43.7 per 1,000 of all diseases, among factory workers - 80.0, chronic bronchitis - 19.3 and 22.8, pleurisy - 6.9 and 7.9. For individual groups of industries for the period from 1888 to 1897, diseases of the olfactory and respiratory organs constituted the following figures (Table 16). Table 16. Morbidity from diseases of the respiratory organs by individual groups of industries (per 1,000 patients). Groups of industries

Groups of industries | Processing of fibrous substances | Mechanical production | Cement industry | Chemical industry | Patients in zemstvo clinics | Total --- | --- | --- | --- | --- | --- | --- Both sexes | 110.9 | 124.0 | 115.6 | 120.0 | 167.5 | 116.8 Men | 78.9 | 59.8 | 70.5 | 110.9 | 93.4 | 101.3 Women | 93.4 | 101.3 | - | - | - | -

A more detailed breakdown of materials by the class "processing of fibrous substances" gives such indicators: cotton processing - «St 128.3, wool - 107.8, silk - 115.2, dyeing production - 109.5 (per 1,000 patients). Based on detailed processing of materials, P. I. Kurkin comes to the conclusion that "one of the most constant signs of the morbidity of the factory population is the higher proportion accounted for by diseases of the olfactory and respiratory organs." From the latest works, Table 17, compiled by S. M. Bogoslovsky (1928) and based on the processing of materials from the examination of the health status of workers and employees of the city of Moscow in the course of dispensaryization, can provide an understanding of the relationship between diseases of the respiratory organs and the professional composition of patients. Table 17. Prevalence of diseases of the respiratory organs in hired labor (per 100 persons in each group).

Groups of hired labor | Diseases of upper respiratory tract | Emphysema of the lungs | Pleurisy --- | --- | --- | --- Men | Women | Men | Women | Men | Women Production workers | 19.6 | 16.8 | 13.8 | 12.9 | 10.2 | 11.1 Auxiliary workers | 4.8 | 6.5 | 3.4 | 1.0 | 1.6 | 0.4 Clerical workers | 1.0 | 1.0 | 0.9 | 0.9 | 0.9 | 0.8

Men in all groups have higher morbidity than women. Among employees, morbidity is lower than among other groups of hired labor. Diseases of the upper respiratory tract are observed more frequently among production workers, emphysema of the lungs - among auxiliary workers, pleurisy - equally among production and auxiliary workers. The relationship between the prevalence of emphysema of the lungs and length of service in hired labor is presented in Table 18 (per 100 persons in each group). Table 18. Length of service

Length of service | Production workers | Auxiliary workers | Clerical workers --- | --- | --- | --- Men | Women | Men | Women | Men | Women Up to 1 year | 0.4 | 0.7 | 0.6 | 0.9 | 6.4 | 0.2 1-5 years | 0.4 | 0.3 | 1.1 | 1.1 | 4.3 | 0.3 5-8 years | 0.3 | 1.6 | 1.3 | 6.4 | 0.3 | 2.4 8 years and more | 0.3 | 1.8 | - | - | - | - Total | 4.8 | 1.0 | 6.0 | 1.6 | 3.4 | 0.4

The relationship between the prevalence of diseases of the upper respiratory tract and length of service in hired labor is presented in Table 19 (per 100 persons in each group). In general, with an increase in length of service, the prevalence of both emphysema and diseases of the upper respiratory tract increases. Data on registered diseases of the respiratory organs in the city of Tver for 1925, according to M. Rozhdestvensky, per 1,000 population are given in Table 20. N. Vasilevsky provides the following figures for loss of working capacity due to diseases of the respiratory organs per 100 insured in the textile industry of the city of Moscow and Moscow province: cases of loss of working capacity - in the city of Moscow among men in 1926 - 4.0, in 1927 - 3.2, among women for the same years - 3.6 and 3.1; in the districts of the Moscow province among men in 1926 - 4.2, in 1927 - 3.3, among women - 2.8 and 2.3. The general coefficient of days of disability from diseases of the respiratory organs for the Moscow province per 100 insured in 1926 - 53, and in 1927 - 35 (in Leningrad in 1925 - 83).

In the processing of cotton, for every 100 insured persons, there are 2.8 cases of disease and 36 days of disability per year for both sexes; in the processing of wool - 3.2 and 29; in the processing of silk - 2.4 and 34. The average duration of one case of disability from diseases of the respiratory organs is 13 days. A number of diseases of the respiratory organs are closely related to the patient's profession; these diseases are predominantly professional. They mainly affect workers in so-called dusty professions, as well as those dealing with toxic vapors and gases, subject to thermal irritations, etc. Professional diseases of the nose and throat are observed, for example, in persons working in textile, tobacco, and flour milling industries (dust hazards), in the chemical industry (toxic vapors and gases), in glass factories, in hot workshops (thermal hazards), etc. For some professions, specific professional diseases are characteristic: for example, ulcers and perforations of the nasal septum are observed in workers of cement plants, chromium production, as well as workers dealing with arsenic, corrosive sublimate, etc. The same causes (dust, chemical and thermal irritations) also cause catarrhal diseases of the larynx and trachea. Among professional diseases of the larynx, one should note the group of diseases in whose etiology excessive strain plays a role (chronic laryngitis in singers, teachers, orators, etc.). Among professional diseases of the bronchi and lungs associated with dust, one should mention bronchial asthma, pneumoconioses (see.)-anthracosis, siderosis, chalcosis, etc.