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Rh and in which small patches of consolidation are usually scattered throughout the lower lobes of both lungs. This broncho- or catarrh all 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 infrequently 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 infiuenzae alone has been found, and the Klebs-Lofiier 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 Tube" or lymph currents. Also in some cases it has been cu,0s, s 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, (IJ) in birds, (0) in rats, (d) in cattle, (e) in man. Exactly how far they 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-pneumonia's are not purely catarrhal in the strict pathological sense. For instance, a considerable amount of fibrinous exudation is not infrequently present in the patches of broncho-pneumonia, and some of the cases of septic broncho-pneumonia can scarcely be accurately termed Cdlllffhdl.
 * The term catarrhal pneumonia has been usually regarded as

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 3. 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 tubercle 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 conhned 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 lungsis by no means infrequent, 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