Chronic Tuberculosis either deposits its product imperceptibly, or else as crises of a mild general disease, with symptoms of moderate vascular excitement, and recurring at intervals. In accordance with this view we find tubercles of various ages and stages; and at the extreme points of the diseased lung-substance we have the two extreme stages of tubercle; at the apices, where the tubercles are first developed, we have caverns; and at the lowest portion we have recent, crude, tuberculous granulations; between these we have dissolved tubercles next to the caverns, and lower down such as are just beginning to soften.

It either proves fatal in the form of phthisis through exhaustion and tabes, or through some of those accidents which we have already described as liable to occur in the course of phthisis, as for instance the supervention of pneumonia with a tendency to tuberculous infiltration (hepatization), hyperaemia or oedema of the lungs, hyperaemia of the brain and serous effusion into its ventricles (hydrocephalus, serous apoplexy), tuberculous meningitis, exudative processes in the neighboring mucous canals, as the trachea or oesophagus, purulent metastases, or the supervention of acute pulmonary or general tuberculosis.

The tuberculous habitus in general, and more especially the irritable scrofulous habitus, are the stamp indicating a predisposition to pulmonary tuberculosis; the torpid scrofulous habitus more commonly gives rise to bronchial tuberculosis. The well-known (phthisical) conformation of the chest which predisposes to pulmonary tubercles, is by no means invariably present; its peculiar relation to tuberculosis is unknown, and any connection between the smallness of the respiratory organs in a contracted thorax, and the development of pulmonary consumption, is only hypothetical. Tubercles are often developed in the lungs of individuals, independently of any marked external influences, and then form constitutional pulmonary tuberculosis and pulmonary phthisis. On the other hand, they may arise independently of this constitutional dyscrasia, in consequence of appreciable noxious influences, which induce either a purely tuberculous condition of the juices, or a modification, that is to say, a combination of this state with some other. This is acquired tuberculosis, which is either pure, or more or less modified and combined, such as follows the exanthemata and impetigo, gonorrhoea, syphilis, and anomalous gout, and occurs in drunkards, after the suppression of normal or habitual discharges, as, for instance, of the menses, after the cure of inveterate ulcers, etc.

The inveterate forms of dyscrasia deposit different varieties of tubercle, which have not hitherto been fully described; they occasionally terminate in hemorrhagic tubercle. The tuberculosis is distinguished from the ordinary forms by commencing at an uncommon part, by its unequally attacking the most different parts of the lungs, by the deposit being accumulated in circumscribed or grape-like branches, by its very considerable amount, and by its peculiar, dirty-gray or leaden color with a greenish sparkling appearance. (See Vol. I).

Cancer of the lungs is sometimes deposited in a form resembling tubercle; we must carefully avoid confounding these morbid growths.

Pulmonary tuberculosis, like tuberculosis in general, is excluded by all the conditions enumerated in the first volume, especially by diseases of the lungs, attended with atrophy, emphysema, bronchial dilatation, excessive condensation, compression, obsolescence or obliteration of the tissue.