The healthy lungs are spongy organs, made up of numerous air-containing vesicles (see p. 143). Under the action of the tubercle-bacilli, small areas of bronchitis or pneumonia develop. Then, in the struggle of the system to " eat up the bacilli " as it were, small nodules (tubercles) appear. These, if present in large number, may become confluent and form hard masses ; and these masses, on decomposing, form cheesy granules, particularly if the bacilli have been killed in the individual granule. The air-containing pulmonary vesicles are gradually encroached upon by the growth of these nodules, and by the resulting bronchitis and pneumonia, so that in terference with respiration is brought about. In the further course of the affection, under the influence of pus-producing bacteria, a softening of the involved parts may take place. As soon as these softened masses perforate a branch of the bronchial tree, they are expectorated. This gradual softening and expectoration of lung-tissue cause the development of pulmonary cavities, which may be as large as a fist, or larger. It is quite obvious that the process of suppuration and disintegration involves the blood-vessels also. In many instances, however, the blood may coagulate in the affected part of the vessel before the wall of the blood-vessel has been perforated ; and when this is the case, no hemorrhage takes place. In other cases the hLemorrhage may be very profuse.
As a rule, the tuberculous changes begin in the upper borders, or apexes, of the lungs—on one side, or on both. It is also usually the case that, in the further course of the disease, the upper parts of the lungs are more severely involved than the lower ones.
When the affection is slight, or when the focus of the disease is located more centrally, surrounded by healthy air-containing tissue, it is often im possible to discover the seat of the disease, either by auscultation (listening for the sounds produced in the lung) or by percussion (tapping) of the thoracic wall. With the increase of the inflammatory processes and of the con solidations, the respiratory sounds, as well as the sounds produced by tapping the chest-wall, are, however, materially changed, thus furnishing means of locating the diseased area. To correctly interpret the importance of these changes, in comparison with the sounds produced by healthy lungs, con stitutes an art of the physician, to whom these methods of examination (auscultation and percussion) constitute a means of obtaining a clear and certain picture of the nature and course of the disease.
The most important factor about tuberculosis is its prevention ; and a consideration of those measures which are best calculated to prevent its development may be detailed to advantage.
The treatment of consumption is a matter for careful consideration by a physician. As has already been emphasised, the tubercle-bacillus is, as a rule, able to obtain a foothold only in a debilitated body or in an organ which is injured. Therefore, by keeping the body in general good health,
hardening it so that it can withstand external, harmful influences (see HAR DENING), it is possible to prevent the appearance of tuberculosis. This care of the health should begin in early childhood, as the youthful body is charac terised by its ready adaptability. The well-to-do, especially, often trespass in this respect by over-indulgence and effeminacy ; whereas the poorer part of the population does so from carelessness or from lack of know ledge, and, it is true, to a great extent also by reason of adverse economic conditions.
Marriage of tuberculous persons deserves special mention. In some communities the law has already advanced so far as to forbid consumptives to contract marriage. This prohibition is partly based on the assumption that the dis emination of tuberculosis is brought about by heredity—if even only of the predisposition to the disease. Such a measure has great advan tages. At any rate, tuberculous patients should consider it an imperative duty to forego marriage, at least so long as cough, night-sweats, general debility, or other symptoms which characterise active progression of the disease, are present. By marrying in spite of these disabilities, tuberculous persons, through their own fault, cause the misfortune of themselves and their progeny. Besides, they themselves are usually accorded only a brief space of life in which to enjoy matrimonial bliss for the struggle for existence, and the worries caused by an increase of the household, cause an increased straining of all faculties, and further the development of this dangerous affection. In the case of the wife, the confinements are an additional aggravating factor. . Consumptives should not marry until the physician assures them that the disease has been arrested ; and even then they should do so only under favourable financial conditions. It would be still more advisable to wait until two years after the disappearance of all symptoms of the disease, in order to be, to a certain extent, secured against recurrences.
Among the preventive measures against tuberculosis, the choice of a suitable vocation deserves the most far-reaching consideration. The choice of a suitable calling may often tend to procure complete health, or, at least, to prolong life for several years ; whereas an unsuitable choice will soon kindle the lurking fire of the treacherous disease into a blazing flame, prematurely ending the life of the affected. Individuals with weak chests, even though they be not predisposed to tuberculosis, are not fit for occupa tions in closed rooms, where they are exposed to irritating dust, gases, or vapours, or where they are called upon to handle poisonous materials. People with tuberculous tendencies should adopt an open-air life, particularly in the fields or woods.