According to the case and the kind of animal affected, the lung presents either disseminated tuberculous formation, tuberculous infiltration, tuberculous conglomeration, or cavern formation.
The lung may be affected to such a degree that it appears incredible that the blood can have been sufficiently aerated to support life.
The lungs may be transformed into yellowish, caseous, calcareous, or softened masses enveloped in thick, fibrous, resistant walls. The intervening pulmonary tissue may be healthy in appearance, or reddened, congested, and sometimes hepatised.
The pleural, pericardial, and peritoneal membranes may be covered with exuberant tuberculous lesions, like ripe mulberries, in consequence of fusion and massing of the tuberculous growths. The primary tubercles are surrounded with fibrous walls, which granulate when on the surface of a serous membrane, and impart to the membrane a vegetative, sometimes villous appearance, and a colour varying from pink to light or dark red.
The collective lesions lining the cavities are described by butchers under the significant term of “grapes.” In the interior of these exuberant masses, which sometimes form layers an inch or more in thickness, the tuberculous lesions undergo the usual developmental changes, that is to say, they become caseated or infiltrated with lime salts, but they do not so readily undergo softening as those of the lung. The parietal and visceral serous membranes readily become adherent at numerous points, setting up union between the lung and the walls of the chest, or the intestine and the walls of the abdomen, etc.
In the pericardium the vegetations are frequently of a fungoid character.
Tuberculosis of lymphatic glands sometimes assumes a disseminated, discrete form or that of a diffuse infiltration, or, again, in old-standing cases it constitutes a massive tuberculous conglomeration. In point of fact, the lymphatic glands as such no longer exist, their tissue having undergone total degeneration; they are represented only by an enlarged, thick, fibrous shell, forming the envelope which encloses caseated and calcareous masses of a more or less soft nature.
Tuberculous infiltration of the submaxillary and sub-parotideal lymphatic glands interferes with swallowing and breathing, compresses the pharynx, œsophagus and larynx, and deforms the head.
Compression of the arteries, veins, nerves, etc., at the entrance to the chest may cause various symptoms which are not difficult to interpret. The glands at the entrance to the chest and the whole of the anterior mediastinum may form a single mass. Lesions in the posterior mediastinum, however, are of even greater importance and explain certain symptoms, such as difficulty in swallowing, spasm of the œsophagus, mechanical contraction of the œsophagus, permanent tympanites, etc., for which the state of the lungs alone would not account.
Even when the lungs are unaffected it may happen that the lymphatic glands of the mediastinum (superior or inferior œsophageal lymphatic glands) and the bronchial lymphatic glands may be so diseased that the œsophagus is completely surrounded and compressed by them, and its function thus seriously impaired (Fig. 276).