The action of inspiration disturbs many organs from the position of rest into which gravity and their own physical properties have thrown them. The ribs and sternum are raised from the position of lowest level; the elastic costal cartilages are twisted; the elastic lungs are put upon the stretch; the abdominal organs,. themselves elastic, are compressed and thrust against the elastic walls of the belly, causing these to bulge outwards. In short the very act of inspiration stores up, as it were, in sundry ways the forces which make for expiration. As soon as the inspiratory muscles cease to act these forces come into play, and the position of rest or equilibrium is regained. It is very doubtful whether any special expiratory muscles are called into action during ordinary respiration. The internal intercostals may in man be exercised in ordinary expiration (although they are certainly not so exercised in the dog and the cat); but in laboured expiration many muscles assist in the expulsive effort. The muscles forming the belly-walls contract and force the abdominal contents against the relaxed diaphragm in such a manner as to drive it farther and farther into the thorax. At the same time by their attachment to the lower edge of the From Hermann's Handbuch. FIG. 9. - Showing Slope of thorax these same muscles pull down the ribs and sternum. The M. triangularis sterni, which arises from the back or thoracic aspect of the sternum and lower costal cartilages and is inserted into the costal cartilages higher up, can obviously depress the ribs. So also can the M. serratus posticus inferior, which arises from the thick fascia of the loins and is inserted into the last four ribs. So also can the M. quadratus lumborum, which springs from the pelvis and is attached to the last rib. Indeed there is hardly a muscle of the body but may be called into play during extremely laboured respiration, either because it acts on the chest, or because it serves to steady some part and give a better purchase for the action of direct respiratory muscles.
Certain Abnormal Forms of Respiration. Coughing. - There is first a deep inspiration followed by closure of the glottis. Then follows a violent expiratory effort which bursts open the glottis and drives the air out of the lungs in a blast which carries away any light irritating matter it may meet with. The act is commonly involuntary, but may be imitated exactly by a voluntary effort.
In this act a current of air is driven from the lungs and forced through the narrow space between the root of the tongue and the depressed soft palate. This action can only be caused voluntarily.
There is first an inspiration which is often unusually rapid; then follows a sudden expiration, and the blast is directed through the nose. The glottis remains open all the time. The act is generally involuntary, but may be more or less successfully imitated by a voluntary effort.
Snoring is caused by unusually steady and prolonged inspirations and expirations through the open mouth, - the soft palate and uvula being set vibrating by the currents of air.
Crying consists of short deep inspirations and prolonged expirations with the glottis partially closed. Long-continued crying leads to sobbing, in which sudden spasmodic contractions of the diaphragm cause sudden inspirations and inspiratory sounds generated in larynx and pharynx.
Sighing is a sudden and prolonged inspiration following an unusually long pause after the last expiration.
Laughing is caused by a series of short expiratory blasts which provoke a clear sound from the vocal chords kept tense for the purpose, and at the same time other inarticulate but very characteristic sounds from the vibrating structures of the larynx and pharynx. The face has a characteristic expression. This act is essentially involuntary, and often is beyond control; it can only be imitated very imperfectly.
Yawning is a long deep inspiration followed by a shorter expiration, the mouth, fauces and glottis being kept open in a characteristic fashion. It is involuntary, but may be imitated.
Hiccough is really an inspiration suddenly checked by closure of the glottis; the inspiration is due to a spasmodic contraction of the diaphragm. The closure of the glottis generally leads to a characteristic sound. (A. G.*) (4) Pathology Of The Respiratory System In the following article we have to give an account of the more important pathological processes which affect the lungs, pleurae and bronchial tubes. In the aetiology of pulmonary affections, the relations between the lungs and the external air, and also between them and the circulatory system, are important. The lungs are, so to speak, placed between the right and left cavities of the heart, and the only way for the blood to pass from the right ventricle to the left side of the heart, except in cases of a patent foramen ovale or other congenital defect forming a communication between the two sides of the organ, is by passing through them. The result is that not only may they become diseased by foreign material carried into them by the blood, but any obstruction to the flow of blood through the left side of the heart tends sooner or later to engorge or congest them, and lead to further changes. Through the nose and mouth they are in direct connexion with the external atmosphere. Hence the variable condition of the air as regards temperature, degree of moisture, and density, is liable to produce directly various changes in the lungs, or to predispose them to disease; and the contamination of the air with various pathogenic germs and irritating particles in the shape of dust, is a direct source of many lung affections.
Bronchitis, or inflammation of the mucous membrane of the bronchial tubes, has been generally attributed to exposure to atmospheric changes. It occurs with great frequence in the extremes of life, and it is in early childhood and in old age that it is more liable to be fatal. Bronchitis may often follow exposure to cold, but that low temperature in itself is not sufficient to cause it is shown by the fact that the crews of arctic expeditions have been singularly free from diseases usually attributed to cold, but on their return to moist germ-laden atmospheres have at once been affected. Children reared in heated rooms with lack of ventilation are peculiarly susceptible to attacks on the slightest change of temperature. Bronchitis is also frequently caused by cardiac and renal diseases, and by the extension of inflammatory diseases of the upper air passages (as rhinitis, laryngitis or pharyngitis), while blockage of the nasal passages by adenoid or other growths may, by causing persistent mouth-breathing, lead to bronchial infection. Before the bacterial origin of disease was understood, bronchitis was attributed solely to what is termed " catching cold, " and the exact relation of the chill to the bacterial infection is still unknown. It is probable that the chilling of the surface of the body by exposure causes congestion of the mucous membrane, the presence of a virulent micro-organism being then all that is required to produce bronchitis. It is generally accepted that in persons living in the pure air of the country the small bronchi and air-cells are sterile (Barthel in the Zentralblatt fur Bakteriologie, vol. xxiv.). Bacteria are arrested on their way by the leucocytes of the nasal mucous membrane and by the vibration of the ciliated epithelium of the upper air passages. The mucous membrane of the upper bronchi is, however, tenanted by various micro-organisms such as the diplo-bacillus of Friedlander, bacillus coli communis, micrococcus tetragenus, &c., and it is considered by William Ewart that these organisms may in certain conditions of their host become virulent. " Specific " bronchitis occurs in the course of a specific infective disease (e.g. influenza, measles or whooping cough) and is due to the specific micro-organism gaining access by the mucous membrane of the respiratory tract. Cases have been known in which the diphtheria bacillus has been so localized. In glanders, small-pox, syphilis and pemphigus, the infective micro-organism is carried to the bronchi by the blood stream. In common or " nonspecific" bronchitis, streptococci, pneumococci and staphylococci are found in the sputum together with Friedlander's bacillus and the bacillus coli communis. Microscopically the bronchi show hyperaemia of the mucous and submucous coats, and the whole wall becomes infiltrated with polymorphonuclear leucocytes and round cells. Many cells undergo mucoid degeneration, and there is abundant epithelial proliferation. A large quantity of mucus is secreted by the glands, and the lumen of the bronchi contains an exudate consisting of mucus, degenerated leucocytes and cast-off epithelial cells.
In the rare form of bronchitis known as fibrinous or plastic bronchitis a membranous exudate is formed which forms casts of the bronchi, which may be coughed up. The casts vary from an inch to six or seven inches in length, with branches corresponding to the divisions of the bronchi from which they come. The cast consists of mucus and fibrin in varying proportions. The exact pathology of this variety is still undetermined.
Bronchitis may affect the whole bronchial tract, or more especially the larger or the smaller tubes. It may occur as an acute or as a chronic affection. In the acute form the inflammation may remain limited to the bronchial tubes and gradually subside, or it may lead to inflammation of the surrounding lung tissue, giving rise to disseminated foci of inflammation of greater or less extent throughout the lungs (catarrhal or bronchopneumonia). This is a common complication of bronchitis, especially where the smaller tubes are affected, and is more frequently seen in children than adults. In cases of chronic bronchitis the affection, as a rule, begins as a slight ailment during the winter, and recurs in succeeding winters. The intervals of freedom from the trouble get shorter, and in the course of a few years it persists during the summer as well as the winter months. A condition of chronic bronchitis is thus established. The persistent cough which this occasions is one of the chief causes of the development of the condition of emphysema, where there is a permanent enlargement of the air-cells of the lungs with an atrophy of the walls of the air vesicles. The emphysema occasions an increase in the shortness of breath from which the person had previously suffered, and later, in consequence of the greater difficulty with which the blood circulates through the emphysematous lungs, the right side of the heart becomes dilated, and from that we have the development of a general dropsy of the subcutaneous tissues, and less and less perfect aeration of the blood.
The death rate from bronchitis in England and Wales during 1908 was: males 1102, females 1083 per million living. The death rate for the five years1901-1905was 12 3 7 per million for all sexes. The death rate for the twenty years1888-1908consistently showed a slight decline.
We all inhale a considerable amount of carbonaceous and other foreign particles, which in health are partly got rid of by the action of the ciliated cells lining the bronchial tubes, and are partly absorbed by cells in the wall of the tubes, and carried in the lymph channels to the bronchial lymphatic glands, where they are deposited, and cause a more or less marked pigmentation of the tissues. Part of such pigment is also deposited in the walls of the bronchial tubes and the interstitial tissue of the lungs, giving rise to the grey appearance presented by the lungs of all adults who live in large cities. In certain dusty occupations, such as those of stone masons, knife-grinders, colliers, &c.,. the foreign particles inhaled cause trouble. The most common affection so produced is chronic bronchitis, to which becomes added emphysema. In some cases not only is bronchitis developed, but the foreign particles lead to an increase of the fibrous tissue round the bronchi and in the interstitial tissue of the lungs, and so to a greater or lesser extent of fibroid consolidation. As this fibrous tissue may later undergo softening and cavities be formed, a form of consumption is produced, which is named according to the particular occupation giving rise to it; e.g. stonemasons' phthisis, knife-grinders' phthisis, colliers' phthisis. It should, however, be pointed out that these dusty occupations are probably not so frequently the cause as was at one time taught of these simple inflammatory fibroid changes in the lungs with their subsequent cavity formation; individuals engaged in such occupations are apt to suffer from a chronic tuberculosis of the lung associated with the formation of much fibrous tissue, and the occupation simply predisposes the lung to the attacks of the tubercle bacillus.
The term pneumonia is frequently used of different forms of inflammation of the lungs, and includes affections which run different clinical courses, present diverse appearances after death, and probably have different excit ing causes. It would be better if the term acute pneumonia or pneumonic fever were reserved for that form of acute inflammation of the lungs which is usually characterized by sudden onset, and runs an acute course, which terminates generally by crisis from the fifth to the tenth day, the inflammation leading to the consolidation by fibrinous effusion of the greater part or whole of one lobe of a lung. Acute pneumonia usually occurs in a sporadic form, and is most prevalent in the United Kingdom from November to March. Occasionally it is epidemic, and there is evidence to show that sometimes it is an infective disease. There is great difficulty, however, in being quite certain that the occurrence of the disease in those who have been attending upon or brought into intimate connexion with sufferers from pneumonia is the result of infection, for such cases may be due to an epidemic of the disease, or to the various individuals attacked having been exposed to the same cause.
Formerly acute croupous or lobar pneumonia was thought to be due to " catching cold "; we now know it to be an infectious disease resultant on the invasion of one or more specific micro-organisms. The chief micro-organisms which have been found to be present during an attack of acute pneumonia are the micrococcus lanceolatus or pneumococcus of Frankel and Weichselbaum, which is found in the inflamed lung in a large majority of cases and is capable of producing pneumonia when inoculated into guinea-pigs. Sternberg demonstrated the presence of the pneumococcus in the saliva of healthy individuals; it tends, however, in this case to vary in form. The micro-organism differs in virulence in given strains; thus one epidemic may be more severe than another; and it tends to increase in virulence in its passage through the human subject. The exact conditions necessary for the production of increased virulence in the organism causing an attack of lobar pneumonia are not yet determined, but are usually ascribed to lowered states of the health and to atmospheric conditions. The pneumococcus produces in the human organism an intracellular toxin, but the question as to whether it can also produce a soluble toxin in the living body is still debated. The difficulty of obtaining sufficient quantities of the toxins of this organism has prevented the production of antisera of high potency. In lower animals, less potent sera have proved successful in protecting against a fatal dose of pneumococci. The change effected by the administration of a serum is produced by causing a change in the pneumococci, which causes them to be more easily destroyed by the phagocytes. The element which brings about this change is termed an opsonin; see Blood and Bacteriology (ii). The bacillus pneumoniae of Friedlander is also said to be found in a certain percentage of cases, but a number of observers deny its presence in pure culture in primary croupous pneumonia.
Unlike many acute diseases, pneumonia does not render a person less liable to future attacks; on the contrary, those who have been once attacked must be looked upon as more prone to be affected again. Acute pneumonia usually attacks the whole or greater part of one lobe of one lung, but more than one lobe may be affected, or both lungs may be involved. The disease produces a solid and airless condition of the affected part owing to a fibrinous exudation taking place into the aircells and smaller bronchial passages. In favourable cases the exudation is partly absorbed and partly expectorated, and the lung returns to its normal healthy condition; in others, death may ensue from the extent of lung affected, or from the spread of the inflammation to other parts, as for instance the pericardium or meninges of the brain. In such cases it is interesting to note that the same micro-organism has been found in the inflammatory exudation in the pericardium or on the meninges as in the pneumonic lung; probably the organism had been absorbed from the lung, and was the cause of the secondary inflammations. In cases of death from uncomplicated pneumonia a very variable extent of lung is involved. In some cases this result may be ascribed to the weakness of the individual and especially of the heart, but in others the virulence of the micro-organisms and the toxins which they have produced is probably the more correct explanation. The improvement in a patient suffering from pneumonia usually commences suddenly, with a rapid fall in the temperature. The day on which this " crisis" takes place varies, but most commonly it appears to be the seventh from the initial rigor (22% of the cases, Jiirgensen). It may, however, occur a few days earlier or later, being observed in about 74% between the fifth and the ninth day of the disease (Jiirgensen). The disease occasionally ends in the formation of an abscess, in gangrene, or in fibroid induration of the lung, but these terminations are rare.
The death rate of acute pneumonia for England and Wales in 1 9 08 was 1383 per million living of the population.
Broncho-pneumonia.-1t is usual to recognize a form of inflammation of the lungs which differs from the above lobar pneumonia.
and in which small patches of consolidation are usually scattered throughout the lower lobes of both lungs. This bronchoor catarrhal' pneumonia is usually preceded by an attack of bronchitis, to which it bears an intimate relation. In some cases the small foci of inflammation may run together so as to affect the greater part of a lobe of a lung, and the distinction between such a form of broncho-pneumonia and lobar pneumonia presents such difficulties in the view of some observers, that they have refused to recognize any essential difference between the two. Usually, however, it is not difficult to distinguish the two affections both clinically and anatomically. Broncho-pneumonia is especially seen as a complication of bronchitis, and while it more frequently attacks children than young adults, it is not uncommon in old people, especially secondary to bronchitis. It is frequent in children after acute infectious fevers, especially measles and diphtheria, and in cases of whooping-cough. It differs from the above-mentioned pneumonia in that it does not usually attack the whole of a lobe of a lung, but occurs in small disseminated patches more especially throughout the lower lobe of both lungs. The accompanying fever is more irregular than in the preceding form, and the disease usually runs a more prolonged course. It is an extremely fatal affection in both the very young and old. Young persons who have suffered from it are not unfrequently attacked by pulmonary tuberculosis subsequently. It must be admitted that we are even less certain of its bacteriology than we are of that of lobar pneumonia. In some cases Frankel's pneumococcus is found, and in others various other micro-organisms. Many of the latter are doubtless saprophytic, and are not the essential cause of the disease, but it is not probable that any one particular form of organism accounts for all forms of broncho-pneumonia.
The bacteriology of broncho-pneumonia presents no one micro-organism which can be definitely said to cause the disease. The micro-organism most frequently found, either alone or associated. with other bacteria, is the pneumococcus, which occurred in 67% of a series investigated by Wollstein. Other organisms found are the streptococcus, particularly in bronchopneumonia following infectious fevers, the staphylococcus aureus and albus, and Friedlander's bacillus. In some cases the bacillus influenzae alone has been found, and the KlebsLolller bacillus in cases following upon diphtheria. When the disease is associated with pulmonary tuberculosis the tubercle bacillus is found.
The tuberculous virus, the tubercle bacilli, may gain entrance to the lungs through the inspired air or by means of the blood or lymph currents. Also in some cases it has been demonstrated that tubercle bacilli may infect the glands of the mesentery following the ingestion of the milk of tuberculous cattle. In this the Government Commissions of Great Britain and Germany as well as the United States Bureau of Animal Industry confirm the findings of private investigators. It may be well here to summarize the views generally held as to infection. In the first place, the doctrine of inherited disease is discredited, and the doctrine of specific susceptibility is in doubt. Infants are known to be extremely susceptible, and this susceptibility lessens with increasing age, adults requiring prolonged exposure. As a mode of infection the sputum of diseased persons is of great importance. Infected food, especially milk, comes next, together with food infected by flies; and the mother's milk is a minor source. Infection is not often received through the skin, but most frequently through the mucous membrane of the mouth, air passages and intestine; occasionally the infection is alveolar. Pulmonary tuberculosis is often secondary to a latent lymphatic form. The tubercle bacillus was discovered by Koch in 1882, and since then it has become generally accepted that the bacillus varies in type. The bacilli have been classified by A. G. Foullerton into (a) occurring in fishes and cold-blooded animals, (b) in birds, (c) in rats, (d) in cattle, (e) in man. Exactly how far they 1 The term catarrhal pneumonia has been usually regarded as synonymous with the term broncho-pneumonia, and this usual nomenclature has been maintained in the present article. We must, however, recognize that all simple acute broncho-pneumonias are not purely catarrhal in the strict pathological sense. For instance, a considerable amount of fibrinous exudation is not unfrequently present in the patches of broncho-pneumonia, and some of the cases of septic broncho-pneumonia can scarcely be accurately termed catarrhal. are interchangeable and can affect the human race is not definitely settled. They may be different varieties of the same species caused by differentiated strains of a common stock, or may be distinct but generically allied species. Von Behring considers that the bovine type may undergo modification in the human body, a theory which may lead to a complete change in our beliefs in the mode of entry of the bacillus. Recent investigators have put forward the view that the tubercle bacillus is not a bacterium, but belongs to the higher group known as streptotricheae or mould fungi.
The action of the tubercle bacillus upon the tissues, like most other infectious agents, gives rise to inflammatory processes and anatomical changes, varying with the mode of entry and virulence of the micro-organism. The most characteristic result is the formation throughout the lungs in the form of small scattered foci forming the so-called miliary tubercles. Such miliary tuberculosis of the lungs is frequently only a part of a general tuberculosis, a similar tuberculous affection being found in other organs of the body. In other cases the lungs may be the only or the principal seat of the affection. The source whence the tuberculous virus is derived varies in different cases. Old tubercular glands in the abdomen, neck and elsewhere, and tuberculous disease of bones or joints, are common sources whence tubercule bacilli may become absorbed, and occasion a general dissemination of miliary tubercles in which the lungs participate. Where the source of infection is an old tuberculous bronchial gland or a " focus of old tubercle in the lung, the pulmonary organs may be the only seat of the development of miliary tuberculosis for a time; but even then, if life is sufficiently prolonged, other parts of the body become involved. Acute miliary tuberculosis of the lungs is not infrequently a final stage in the more chronic tuberculous lesions of the different forms of pulmonary phthisis.
In pulmonary phthisis, or consumption, the disease usually commences at the apex of one lung, but runs a very variable course. In a large majority of cases it remains confined to one small focus, and not only does not spread, but undergoes retrograde changes and becomes arrested. In such cases fibrous tissue develops round the focus of disease and the tuberculous patch dries up, often becoming the seat of the deposit of calcareous salts. This arrest of small tuberculous foci in the lung is doubtless of very frequent occurrence, and in post mortem examinations of persons who have died from injuries or various diseases other than tubercle it is common to find in the lungs arrested foci of tubercle, which in the majority of instances have never been suspected during life, and probably have occasioned few, if any, symptoms. It has been shown that in more than 37% of persons, over 21 years of age, dying in a general hospital of various diseases, there is evidence of arrested tubercle in the lungs. As such persons are chiefly drawn from the poorer classes, among whom tubercle is more common than among the well-to-do, this high percentage may not be an accurate indication of the frequency with which pulmonary tubercle does become arrested. It does, however, show that the arrest and the healing of tuberculosis of the lungs is by no means unfrequent, and that it occurs among those who are not only prone to become infected, but whose circumstances are least favourable to the arrest of the disease. These facts indicate that the human organism does offer a resistance to the growth of the tubercle bacilli.
A focus of pulmonary tubercle may become arrested for a time and then resume activity. In many cases it is difficult to say why this is so, but often it is clearly associated with a lowering in the general health of the individual. It cannot be too strongly insisted that the arrest of a tuberculous focus in the lung is a slow process and requires a long time. Commonly a person in the early stage of phthisis goes away to a health resort, and in the course of a few weeks or months improves so much that he returns to a densely populated town and resumes his former employment. In a short time the disease shows renewed activity, because the improved Tuberculosis. conditions were not maintained long enough to ensure the complete arrest of the disease.
Instead of the tuberculous focus becoming arrested, it may continue to spread. The original focus and the secondary ones are at first patches of consolidated lung. Later, their central parts soften and burst into a bronchus; then the softened portion is coughed up, and a small cavity is left, which tends gradually to increase in size by peripheric extension and by merging with other cavities. This process is repeated again and again, and sooner or later the other lung becomes similarly affected. At any stage of the softening process the blood vessels may become involved and give rise by rupture to a large or a small haemorrhage (haemoptysis). It not unfrequently happens that such haemoptysis may be the first symptom that seriously attracts attention. At a later period haemorrhage frequently takes place in large or small amounts from the rupture of vessels, which frequently are dilated and form small aneurysms in the walls of cavities. A fatal termination may be hastened by the absorption by means of the blood vessels and lymphatics of the tuberculous virus from some of the foci of disease, and the occurrence therefrom of a local miliary tuberculosis of the lungs or a general tuberculosis of other organs. The rapidity with which the destructive process spreads throughout the lung varies considerably. We therefore recognize acute phthisis, or galloping consumption, and chronic phthisis. In the acute cases the softening progresses rapidly and is associated with the development of very little fibrous tissue; probably various forms of microorganisms other than the tubercle bacilli assist in the rapid softening. In the more chronic cases there is development of much fibroid tissue, and the disease is associated with periods of temporary arrest of the tubercular process.
The expectoration from cases of pulmonary phthisis contains tubercle bacilli, and is a source of danger to healthy individuals, in whom it may produce the disease. Attendance on persons suffering from pulmonary phthisis involves very little risk of infection if proper care is taken to prevent the expectoration becoming dry and disseminated as dust; perfect cleanliness is therefore to be insisted upon in the rooms inhabited by a phthisical person. The tubercle bacilli soon lose their virulence in the presence of fresh air and sunshine, and therefore these agents are not only desirable for the direct benefit of the phthisical patient, but also are agents in preventing the development of fresh disease in healthy individuals.
Although the tubercle bacilli are the essential agents in the development of pulmonary tuberculosis, there are other conditions which must be present before they will produce the disease. It is probable that large numbers of individuals are exposed to the action of tubercle bacilli which gain entrance to the pulmonary tract, and yet do not give rise to the disease, because the conditions of their growth and multiplication do not exist. In such cases we may consider that the seed is present, but that the soil is unsuitable for its growth. Certain families appear more predisposed to tuberculosis than others.
The most important circulatory disturbances met with in the lungs are those seen in cases of dilated heart, with or without disease of the mitral valve, when engorgement of the pulmonary vessels sets up a condition of venous engorgement of the lungs. This may lead to various changes. After it has lasted a variable time, and if it is very intense, serous transudation occurs into the substance of the lung and the alveoli, and thus a condition of pulmonary dropsy or oedema is established. The venous engorgement also predisposes the subjects of such heart affections to bronchitis and pneumonia. In disease of the mitral valve, in cardiac dilatation and in simple feebleness of the heart, such as is seen in old age and after debilitating fevers, especially typhoid, there is commonly developed a venous congestion of the bases of the lungs, forming the so-called hypostatic congestion of those organs, and to this is frequently added pneumonia. In long-standing cases of pulmonary congestion brought about by disease of the mitral valve and dilatation of the heart, a certain amount of fibrous tissue may be found in the interstitial tissue of the lungs, and from transudation of certain elements of the blood we get the formation in the newly formed fibrous tissue of blood pigment. In these cases blood pigment is found in the cells, in the pulmonary alveoli, and such cells also carry the pigment into the interstitial tissue. This condition constitutes the state known as brown induration of the lungs. Acute congestion of the lungs occurs as part of the first stage of pneumonia. It also probably exists during violent exertion, and may possibly be brought about by excitement.
Another circulatory disturbance of great importance is that arising from blocking of the pulmonary artery or its branches by an embolus or a thrombus. Where the obstruction takes place in the main vessel, death rapidly ensues. Where, however, a small branch of the vessel is occluded, as frequently occurs from a bows. coagulum forming in the right side of the heart, or in the pulmonary vessels in cases of disease of the mitral valve, or in dilatation of the heart, or from the detachment of a small vegetation from disease of the tricuspid or pulmonary valves, a haemorrhagic exudation takes place, forming a patch of consolidation in the lung (haemorrhagic infarct). As this haemorrhagic exudation takes place not only into the substance of the lung, but also into the bronchial tubes, such lesions are usually associated with spitting of blood (haemoptysis). The increased tension produced in the pulmonary vessels in cases of mitral disease may also probably lead to the formation of haemorrhagic exudations into the lungs, apart from the occurrence of embolism or thrombosis. Usually the occurrence of pulmonary embolism and the formation of haemorrhagic infarcts in the lungs mark an important epoch in the course of a case of heart disease. It usually occurs at a late stage of the affection, and not unfrequently contri butes materially to a fatal termination. It is probable that many of the cases of pneumonia and pleuritic effusion, coming on in cases of valvular heart disease and of cardiac dilatation, owe their origin to an embolus and to the formation of a haemorrhagic infarct.
The term asthma is commonly applied to a paroxysmal dyspnoea of a special type which is associated with a variety of conditions. In true spasmodic asthma there may be no detectable organic disease, and the paroxysms are generally believed to be due to a nervous influence which, acting upon the bronchial muscles, produces a spasm of the tubes, or, acting through the vaso-motor branches of the sympathetic, produces a congestion of the bronchial mucous membrane. The most probable theory is that lately advanced, that it is caused by a profound toxaemia. An organism has been isolated, which is said to be the cause of certain cases of asthma, and the fact that benefit has been said to follow treatment by a vaccine is in favour of this view. The exciting cause may not be at all apparent, even on the most careful observation and examination of the sufferer, but in other cases the attacks may be brought about by some reflex irritation. Nasal polypi and other diseases of nasal mucous membrane have been shown in some cases to be a cause of asthma. Irritation of the bronchial mucous membrane appears to be one of the most common, but it is usually difficult to say exactly in what the irritation consists.
The sputum in true asthma is typical, consisting of white translucent pellets like boiled tapioca. These pellets consist of mucus arranged in a twisted manner and known as Curschmann spirals; they also contain Charcot-Leyden crystals, degenerated epithelium and leucocytes, of which the majority are eosinophiles. The spirals consist of a central solid thread round which the mucus is arranged in spiral form. The twisting has been attributed to a rotatory motion of the cilia, helped by the spasm of the bronchial muscles. Allied to true asthma is the bronchial asthma frequently met with in the subjects of bronchitis and emphysema. In such cases the irritation evidently proceeds from the inflamed bronchial mucous membrane. Hay asthma is the variety in which the pollen of certain plants, especially grasses, is the exciting cause of the paroxysms. In cardiac feebleness, in valvular disease of the heart, and in cardiac dilatation, we may get dyspnoeic attacks of a more or less paroxysmal nature, to which the term cardiac asthma has been applied. Similarly, to a form of dyspnoea met with occasionally as a manifestation of uraemia in chronic Bright's disease the term of renal asthma has been given.
Pleurisy, or inflammation of the pleura, is a very common affection, and is met with under different forms. In many. instances we have simply the pouring out, over a greater or less area of the surface of the pleura, of a fibrinous exudation which may become absorbed or undergo organisation, a certain amount of thickening of the pleura, and adhesions of the two layers resulting. Such cases form the group known as cases of dry pleurisy. In other instances a greater or lesser amount of serous exudation takes place into one or other pleural cavity, forming the cases of serous pleuritic effusion. In others the exudation into the pleural cavity is purulent, giving rise to the condition known as empyema or purulent pleuritic effusion. The occurrence of dry pleurisy is probably very frequent, and leads to small pleural adhesions which cause little or no inconvenience. In post-mortem examinations of persons who have died from various diseases it is common to find such pleural adhesions present, although they have never been suspected during life. Pleurisy in one or other of the above forms may come on in a person apparently in good health (idiopathic pleurisy), or it may follow a fracture of the ribs or other injury to the chest. It is not uncommonly secondary to some other disease; thus it is almost a constant accompaniment of acute lobar pneumonia. In such cases the effusion is most commonly a simple fibrinous one, which with the subsidence of the primary disease is in great part absorbed. In other cases of pneumonia we get a certain amount of serous effusion into the pleura; and sometimes, especially in children, the pneumonia is followed by the development of an empyema. Pleurisy with effusion is also frequently a complication of valvular heart disease and dilatation of the heart, and in such cases is often associated with the formation of superficial pulmonary infarcts. It is also seen in many other diseases of the lungs. For instance, in chronic pulmonary phthisis pleuritic adhesions over various parts of the lungs are the rule; and we also frequently get serous effusion into the pleura as a complication of the various forms of pulmonary tuberculosis. Purulent effusion is less common in phthisis, but it is the rule where the pleura is perforated by the necrosis of a tuberculous focus in the lung and the establishment of a communication between the pleura and a tuberculous cavity and the bronchial tubes (pyopneumonothorax), a combination in which there is both air and pus in the pleural cavity. Secondary pleurisy is also seen in an extension of the disease from neighbouring parts, as from peritonitis, sub-diaphragmatic abscess, and suppuration in the liver or spleen. As a secondary disease, pleurisy is also known in the course of various forms of nephritis, rheumatism, and the acute specific diseases.
Cases formerly classed as idiopathic pleurisy are now known to be caused by certain micro-organisms. These vary in relation to the character of the effusion. The most frequent is the tubercle bacillus, which is generally present in sero-fibrinous effusions. In this case the pleurisy is really secondary to a possibly unrecognized tuberculous infection either of the lung or pleura. In purulent effusions the pneumococcus may occur as a pure infection, or the streptococcus pyogenes or the staphylococcus may be present. Mixed infections occur in 2r % of purulent effusions, and varieties of other organisms, such as the influenza bacillus, the typhoid bacillus, the Klebs-Leffler bacillus and the colon bacillus, have been occasionally found.
There are at least five types of pulmonary emphysema; (I) hypertrophic, idiopathic or large-lunged emphysema; (2) senile or small-lunged emphysema; (3) compensatory emphysema; (4) acute vesicular emphysema; (5) interstitial or interlobular emphysema. Two points are usually admitted: that emphysema appears only in lungs that are congenitally weak, and that the exciting cause is increased intravesicular tension. When one or more lobules are cut off from the working part of the lung the neighbouring vesicles become distended.
Should the plugging of the lobule remain permanent, typical emphysema results. This happens in illnesses inducing violent respiratory efforts, such as chronic bronchitis, whooping cough and asthma. In large-lunged emphysema the lung is excessively large, and does not collapse on opening the chest wall. Microscopically two lesions are notable. The septa between the vesicles are atrophied, many have disappeared and the vesicles have coalesced; the loss in lung tissue diminishes the vascular field of the lung and tends to imperfect aeration, whence the dyspnoea. The elastic tissue of the lung is also lost. In smalllunged emphysema there is a condition of senile atrophy. The lung is smaller than normal, and the intravesicular septa are destroyed. In this case the primary cause is atrophy of the bronchi, and increased air pressure is not a factor. Compensatory emphysema is that which develops in a portion of a lung in which the other portion is the seat of a lesion, such as pneumonia. Occasionally it is merely physiological, but sometimes here too the septa undergo atrophic changes. Acute vesicular emphysema is hardly a pathological variety, and is really rapid distension coming on during an attack of asthma or angina pectoris. The variety is temporary only. Interstitial emphysema is characterized by the presence of air in the interstitial connective tissue of the lung. It is usually due to rupture of the air vesicles during paroxysms of coughing.
(T. H.*; H. L. H.) (5) Surgery Of The Respiratory System About the middle of the igth century, Manuel Garcia demonstrated the working of the vocal cords in the living subject, by placing a flat mirror of about the size of a shilling at the back of the mouth, and throwing strong light on to it from a concave mirror fixed upon the observer's forehead. By the use of a laryngoscope and a cocaine spray the most irritable throat can now be made tolerant of the presence of the small mirror, and thus the medical man is enabled to make a prolonged and thorough examination of the interior of the larynx and even to perform delicate operations upon it. Foreign bodies which have become caught in the larynx can thus be seen and extracted, and small growths can be satisfactorily removed even from the vocal cords themselves.
A foreign body in the air-passages may be impacted above the vocal cords, and the prompt thrusting down of a finger may dislodge it and save the person from death by suffocation. If there is doubt as to the site of the impaction, and the symptoms are urgent (as is likely to be the case) immediate laryngotomy should be done. In this operation a tube is introduced through the crevice which can easily be felt in the middle line of the neck, between the thyroid and cricoid cartilages. The procedure is easily and quickly accomplished. It is, moreover, of ten resorted to when the surgeon is about to perform some extensive operation in the mouth which must needs be accompanied by free haemorrhage. Laryngotomy having been done, and the pharynx having been plugged with gauze, the air passages can be kept free of blood during the whole operation.
If the foreign body be such a thing as a button, cherry-stone, sugar-plum or coin, it may at once set up alarming symptoms of spasmodic suffocation. But when the first alarm has quieted down, the attacks are likely to be only occasional, as when the article, drawn up with the expired air, comes in contact with the under aspect of the vocal cords. It may be that in a violent fit of coughing it will be expelled, but, if not, the surgeon must be at hand ready to perform tracheotomy when the urgency of the symptoms demands it. Tracheotomy is the making of an opening into the trachea, the air-tube below the larynx. It is unsafe to leave a child with a foreign body loose in its windpipe, on account of the risk of sudden and fatal asphyxia. Possibly the X-rays may show its exact position and give help in its removal. But, in any case, the safest thing will be to perform tracheotomy and to leave the edges of the opening into the windpipe wide asunder, so that the object may be coughed out - the nurse being on guard all the while. The operation of tracheotomy is sometimes urgently called for in the case in which the air-way has become blocked by a child having sucked hot water from the spout of a kettle or teapot, or in the case of obstruction by the swelling of the acute inflammation of laryngitis or of diphtheria. Should the air-way through the larynx become narrowed by the presence of a growth which does not diminish under the influence of iodide of potassium, the question may arise as to whether it should be dealt with by splitting the thyroid cartilage and holding the wings apart, or by the removal of the whole larynx. For such growths are often malignant. If the wide infection of the lymphatic glands of the neck suggests that no radical operation should be undertaken, a bent silver tube may be introduced below the growth (tracheotomy) in order to provide for the entrance of air. This will get over the difficulty of breathing, but it cannot, of course, do more than that.
Acute laryngitis is very often due to diphtheria. The symptoms are those of laryngeal obstruction, together with constitutional disturbances of various kinds. The old-fashioned nurse called the disease " croup " - a term devoid of scientific meaning (see DIPHTHERIA). In an ordinary catarrhal case, leeches and fomentations may suffice, though sometimes tracheotomy or intubation is called for. But if bacteriological examination shows the presence of diphtheritic bacilli, antitoxin must at once be injected. (See also LUNG.) (E. 0.*)
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