A consolidation is merely an aggre gation of tubercles, or the tubercular process in which all the tissue of that area is involved with little or no normal structure sandwiched in between.
If these minute tubercular masses be come scattered throughout the lung so that normal tissue-elements intervene, the picture of an infiltration presents it self. When the disease progresses, with consequent diminution of the normal ad jacent structure, the process is spoken of as passing from the stage of infiltration to that of consolidation. The pathological change is practically the same, the chief difference depending upon the amount of tissue involved, and whether the proc ess be diffused or localized. True con solidation is considered a later stage of infiltration, because it is a degree nearer to the breaking-down process; but the chief reason for this breaking down is that the mere aggregation of these tubercles, these non-vascular, cellular bodies of low vitality, cuts off nutrition from the interior of its own mass, in consequence of which softening takes place. An infiltration shows no such tendency, because nourishment is de rived from the intervening normal ele ments, sufficient to keep the area from undergoing destructive changes. The bronchopneumonia of acute or gallop ing consumption may be considered a tubercular invasion similar to the rest, but lacking the picture of more definite arrangement into tubercles, because the process has been severe and sudden, and has brought forth more of the acute in flammatory products, and because the defensive tissue-cells have failed to ar range themselves in the usual order oh served in the more chronic lesions. However, in following these cases of galloping consumption it is not uncom mon to see the process limited, the pict ure assuming that of chronic ulcerative phthisis; which means that the tissues have reacted, and the invading broncho pneumonic area has had thrown around it a protective layer or epithelioid cells, and a similar layer of leucocytes. In other words, a tubercle has been formed, which is Nature's effort at limitation, and her first step toward making of it a foreign body, her only method of cure, which in turn is accomplished by the fibrous capsule thrown out around it.
In chronic ulcerative phthisis there may be seen at the same time all kinds of le sions; miliary tubercles; areas of bron cho-pneumonia; caverns of various sizes and shapes, sometimes communicating with one another, undermining the greater part of a lobe or lung. Travers ing the walls of these cavities are fre quently seen arteries which, owing to lack of support, have developed upon them aneurismal which subse quently rupture and give rise to hemor rhage. These cavities may be either dry, representing a healed process, or they may contain muco-pus or pus, and have lining them a pyogenic membrane. The bronchial glands in pulmonary tubercu losis are frequently invaded; they may show infiltration, areas of caseation, or may become impregnated lime salts. The pleura is usually involved, and the entire sac may be obliterated; a caseating mass may rupture into the cavity instead of a bronchus, and give rise to an empyema or pyopneumothorax.
PIITHISIS.—Fi broid phthisis, as its name implies, is a condition in which there is a preponder ance of the fibrous element; it fre quently commences as a pulmonary cir rhosis upon which later the tubercular process is superimposed; in many in stances it is tubercular from the begin ning. Owing to fibrous contraction, there is marked diminution in the size of the affected lung; the thorax caves in to fill the space caused by shrinkage of the organ, which leaves a larger area of chest-wall exposed to the apex-beat when the change affects the left lung. The disease may last for years and the patient enjoy, during that time, fairly good health; there is usually dyspncea on exertion. With the formation of cavities the usual physical signs appear, and more or less profuse expectoration occurs, which may, owing to its reten tion, become foul and undergo putrefac tive changes—causing a horribly-offen sive odor. Erosion of blood-vessels gives rise to frequent hemorrhages, which may finally prove fatal. There is little absorption, owing to the effectiveness with which the process is shut off from the general system, and, consequently, no fever. Amyloid changes are common.