In cases where the disease consists principally of the grey and yellow miliary nodules, these bodies are seen grouped in clusters and more or less closely aggregated. They are more numerous towards the apex ; but sometimes the whole of both lungs may be seen to be stuffed with them ; and in some parts, in addition, there may be softening cheesy masses, more or less disintegrated. In most cases the lungs are also found to be the seat of increased fibrosis, and some dilatation of the smaller air-tubes can be perceived.
The real tubercular phthisis attacks both lungs simultaneously. The catarrhal form begins in one lung, and it is not until signs of softening are noticed that the opposite lung becomes affected. This softening of the cheesy matter in the affected lung is often a signal for a more general diffusion of the disease. The apex of the opposite lung is attacked, and caseation and softening occur in the glands of Pet'er's patches and in the solitary follicles in the neighbourhood of the ilio-cwcal valve, giving rise eventually to ulceration of the bowels.
On microscopical examination of the lungs, the seat of pulmonary phthisis, various histological changes are discovered. According to Dr. T.
Henry Green, these are mainly of four kinds : 1st, a filling of the pul monary vesicles with fibrinous exudation and leucocytes ; 2d, an accumula tion of large epithelial cells within the alveoli ; 3d, an infiltration and thickening of the walls of the air-vesicles, and often also of the terminal bronchi with small cells ; 4th, an increase of the interlobular connective tissue. These various changes occur in varying degrees in different cases, but all of them are said to be present in the majority of instanceg, although in very different proportions. • In a practical treatise it is unnecessary to enter minutely into the various pathological changes which combine to make up a case of pul monary phthisis ; and the reader is referred to the standard works on pathological anatomy for fuller information upon this subject. The pre ceding sketch is necessarily brief and imperfect ; but some reference to the conditions which give rise to the signs and symptoms about to be enumerated was indispensable.
The acute and chronic forms of pulmonary phthisis will be described separately.