The lungs are almost always affected. They may be involved in every part from the bronchial mucous membrane to the pleura. The changes may be simply those of catarrh or more frequently broncho pneumonia with vicarious emphysema. The pneumonia may follow an extension of the catarrhal process, or it may have its starting-point in the formation of infarcts in the blood vessels. Fibrinous, luemorrhagic or serous exudates in the pleural cavity arc of frequent occurrence. Sometimes latent tuberculosis of the lymph-nodes becomes lighted up as a sequel. In addition to pneumococci and streptococci, diphtheria bacilli are also found in the lesions.
As a rule the heart shows hardly any perceptible changes macro scopically. It is in diastole and the cavities are filled with firm, fibrin ous clots. The heart-muscle is pale, grayish brown and on section, whitish, somewhat oedematous and brittle. In almost every case the microscope shows decided changes in the myocardium. In rapidly fatal cases there is only decided fatty degeneration. When the cases run a longer course the changes are more severe, consisting of disappearance of the transverse striations, massing together of fat granules (in high degree only when severe anaemia has existed), vacuole formation, with fragmentation of the muscle bundles. In IS cases of postdiphtherit.ic heart-paralyses Eppinger found destruction of the muscle fibres result ing from a solution of the cell substance, myolysis, with frequent block ing of the attendant muscle-capillaries by destroyed blood corpuscles. The changes most frequently found are those affecting the interstitial tissue with or without involvement of the parenchyma at the same time, consisting of oedema with an aggregation of lymphocytes and fibroblasts. As a result of degeneration of the heart-muscle and con nective tissue overgrowth, fibrous myocarditis may develop. In the endocardium primary necrosis is not rare with thrombus-formation fol lowing. In the vessels of the heart, as in the other organs proliferation of the intima sets in (see Plate 23).
Disturbances of the kidneys from the simplest to the severest forms are found in all cases. The kidneys are usually somewhat enlarged, pale, with the cortex thickened, the medullary substance showing red dish streaks, and the organ as a whole firm, tough, glistening and moist.
Microscopically about two-thirds of the cases show exclusively or at least principally a degeneration of the epithelium, especially of the con voluted tubules and the descending Henle's loops. For the most part the cells are non-granular, swollen and containing fat-droplets, and in many places they are so completely destroyed that only mass remains (Diphtheritic parenchymatous nephritis, Plate 23). Nu merous hyalin casts are seen in the collecting tubules (Heubner). Intersti tial changes, massing of cells in the blood vessels and infiltration of the connective tissue as well as the very rare involvement of the glomeruli, are found almost solely in older children after a protracted course of the disease. Exceptionally, hremorrhage into the tubules and chronic pro cesses in the form of atrophy are found (Councilman, Mallory and Pearce).
The liver is large, glistening, blood-red, firm and moist, with the acini visible, and on microscopic examination shows decided paren chymatous degeneration.
The spleen shows nothing macroscopically except swelling of the follicles. Microscopically there are seen hyalin degeneration of the arteries and foci of epithelioid cells.
The peripheral nerves show in many cases fatty degeneration of the medullary sheath with swelling and disappearance of the axis-cylinder (degeneration starting from the medullary sheath) and an overgrowth of connective tissue.
Types of the to the location, distinction is made between diphtheria of the pharynx, nose, larynx, vulva, con junctiva and of the skin, or wound-diphtheria. The most frequent variety is diphtheria of the pharynx, which usually appears in a local ized, favorable form, but it may show a progressive character with more or less toxic symptoms, or it may assume a highly malignant gangrenous type. Ordinarily a case shows the triad of symptoms, necrosis of the mucous membrane, fibrinous exudation and presence of the Lorner bacilli. Transitional forms are often seen.