In addition to the cases where tuberculosis is excited in the bodies of persons predisposed to the affection by febrile disturbances or unwhole some conditions of life, there are other instances where the disease appears to be set up by a local infective process. It has been well established by numerous experimenters that the inoculation of tuberculous matter into the bodies of healthy animals will produce general tuberculosis ; and it is held by Koch and his followers that the infecting agent in such cases is the minute organism known as the "tubercle bacillus." Un til lately it was believed that the inoculation into a healthy animal of non-tuberculous or putrid matters would give rise to the formation in the system of a body indistinguishable by the microscope from the gray granu lation. But recent investigations have made it evident that some fallacy must have been present in the experiments which appeared to establish this result ; for a repetition of the experiments by competent observers have shown that no ill consequences of any kind may follow the intro duction of such matters under the skin. Still, arguments drawn from experiments upon animals, especially upon the rodentia, which are usually selected for these investigations, are not perhaps strictly applicable to the human subject. In man the presence of softening cheesy matter in any part of the body may set up an infective process which is indicated by fever, wasting, and symptoms of general distress, and eventually by signs indicating implication of special organs. After death a general distribu tion of small nodules which have all the characters of the gray granulation is found in various organs. In children a chronic empyema often induces such a condition, and the child usually dies with the symptoms of tuber cular meningitis. Acute tuberculosis may be also set up by other forms of cheesy degeneration. Softening caseous glands and cheesy pneumonia are common exciting causes of the disease ; indeed, the scrofulous habit of body appears in itself to be a favouring influence, and the tissues of such subjects furnish a congenial soil in which the growth of the tubercular bodies can be readily excited. The share taken by the tubercle bacillus in the production of tuberculosis—whether it is the sole medium by which the infection is conveyed, as is maintained by some, or is merely a casual addition to the septic agent, as is believed by others—is still at the pres ent moment a matter of warm debate.
Morbid Anatomy.—The distribution of the gray granulation is very frequently general in the child. In the infant it is almost always so : in older children it may be limited to one or more cavities of the body.
Rilliet and Barthez have commented upon the curious fact that while in the adult, according to Louis' canon, if tubercle exist anywhere in the body it will be found also in the lungs, in the child the lungs sometimes escape altogether although every other part of the body is attacked. When found in one cavity of the body alone, the part affected is usually the skull or the abdomen.
The gray granulation is a firm, gray, translucent, projecting nodule which varies in size from a fine pin's head, or even a smaller object, to a millet seed. In Children the colour very quickly changes to yellow and the translucence disappears, so that whatever organ is examined gray and yellow nodules (the latter usually predominating) are found mixed to gether. The growth occurs, according to Rindfleisch, as the result of a
specific irritation of the endothelia of the lymphatics, the serous mem branes, and the blood-vessels, especially the former ; and the nodules are found to follow the ramifications of the finer arteries because the lympha tics run chiefly in the adventitia of the blood-vessels. On careful exami nation the miliary bodies can be seen growing upon the fine vessels, in volving the whole calibre of the channel in the smallest arteries, and in those a degree larger protuberances on one side. Rindfleisch de scribes the granule as a product of inflammation, and states that it consists in an increasing accumulation of leucocytes in the connective tissue of the part irritated. Of these white cells a portion take on an epithelioid char acter. These grow to three or five times the size of a white blood corpus cle and are called tubercle cells. Others develop into the irregular branching bodies called " giant-cells." The giant-cells are not, however, as was at time supposed, peculiar to tubercle. Schiippel believes that they arise within a blood-vessel from the accumulation and adhesion of tenacious masses of molecular matter. When they have reached a size which causes distention of the vessel, nuclei begin to appear. According to this observer, the epithelioid cells are derived from processes of the giant-cells. They lie around the latter and constitute the greater part of the nodule. According to most observers, a section of the tubercles, after they have been some time in existence, shows a delicate reticulum, the meshes of which contain the cells. This, however, is denied by others.
In proportion as the tubercular body enlarges by accumulation of cells the central part is found to degenerate, and when examined at this stage (i.e., after degeneration has begun) it will be seen to consist in great meas ure of small, shrivelled, and granular cells.
The presence of the gray granulation in any tissue is usually quickly followed by inflammation in the neighbourhood of the growths. In the case of a serous membrane, such as the meninges of the brain or the peri toneum, lymph is quickly thrown out, and, if time be allowed, becomes caseous. In the lungs an early consequence is bronchitis and catarrhal pneumonia. In these organs the granules very quickly become yellow and caseous, and every stage of degeneration of the nodules is usually to be discovered. Dr. Wilson Fox has described in the lungs of children dead from tuberculosis : gray translucent granulations ; opaque white gran ules—soft, but of varying firmness and resistance ; the same, but caseous in the centre ; yellow granulations, very soft and easily crushed ; cheesy granules--dry, opaque, and friable, with or without a surrounding zone of gray transparent matter ; groups of the latter forming little masses the size of a pea, bean, or even walnut ; indurated pigmented granules, single or in groups ; and, lastly, tracts of variable size and irregular outline, granular on the surface, passing insensibly into the so-called " gray infil tration." Sometimes, also, he noticed little cavities from softening of the tubercular masses. There were, in addition, signs of secondary catarrhal pneumonia and its consequences.