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Rh 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 IO83 per million living. The death rate for the five years 1901-1905 was 1237 per million for all sexes. The death rate for the twenty years 1888'I9OS consistently showed a slight decline.

Diseases of Occupations.-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 pimp run different clinical courses, present diverse appearmon, , ances after death, and probably have different exciting causes. It would be better if the term acule pneumonia or pneumonia 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 greaser 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 micro coccus 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 pneumonia of Friedliinder 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 exudationfis 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 pneumonia 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, Iiirgensen). 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 1908 was 1383 per million living of the population., Broncho-pneumonia.-jlt is usual to recognize a form of inflammation of the lungs which differs from the above lobar pneumonia.