ary infection occurring either from within the body or through infected aspirating-instruments from without the body. When a transition of the latter kind occurs the exudate is seen to become more and more turbid; the number of pus-corpuscles gradually increases until the liquid is quite purulent. Spontaneous discharge of empyema most frequently takes place through the lung and bronchi, More rarely rupture occurs through the chest-walls anteriorly between the ribs. When rupture has occurred through the lung and bronchi the fistulous communication may remain open and pneumothorax may ensue.

The pleura in empyema shows more or less abundant granulations, which in case of discharge of the liquid serve eventually to unite the costal and pulmonary pleura by firm fibrous adhesions. Occasionally the pus may be completely absorbed, or it may undergo gradual inspissation, remaining as a more or less cheesy detritus, which may finally become calcareous. Such terminations, however, are rare.

Hemorrhagic pleuritis is generally the result of tuberculous infection or of malignant disease of the lungs and pleura. Pleuritis may also take a hemorrhagic form in old and cachectic individuals, or in persons suffering from scurvy, purpura, and similar diseases. As a rule, the liquid is serous, with considerable admixture of blood, but in tuberculous and malignant pleuritis it is sometimes well nigh pure blood.

Chronic Pleural Thickening. This term is used to include cases of thickening of the pleural membrane following various forms of pleurisy, and also cases of a progressive productive character. To the latter the term chronic pleurisy is, strictly speaking, more properly applicable. In either case the pleura is thickened by fibrous overgrowth, sometimes uniformly, at other times in the form of localized thickenings or adhesions. The subpleural pulmonary tissue may become implicated. Eventually the thickened pleura contracts, and if adherent to the chest-wall may cause retractions. The pulmonary tissue is compressed, but the bronchi not rarely become atelectatic.

Associated Lesions in Other Parts.-Though pleuritis is frequently the result of acute or chronic affections of the lung, it often occasions secondary disorders in the latter organ. The subpleural lymphatics are commonly distended with cells, and the inflammatory process may extend for considerable distances along these channels into the interlobular septa of the lung. In empyema the resulting purulent lymphangitis and perilymphangitis lead to striking pathologic appearances (see Pneumonia). The lung also suffers from direct pressure in serous and purulent pleuritis. If the compression to which it is subjected is not relieved by absorption of the liquid, or by its removal by aspiration, the alveolar epithelium degenerates and proliferative inflammation.

takes place in the connective tissue, so that a permanent contraction of the lung results. The removal of the liquid at this stage is not followed by the return of the lung to its proper size and function. On the contrary, the removal or absorption of the liquid in these cases, especially when they occur in young children, causes a sinking in of the ribs and curvature of the spinal column, and the heart and other adjacent organs may be permanently displaced. Most remarkable deformities of the chest may occur. Less extensive contraction of one side of the chest, or displacement of the heart, may result from the contraction of bands of adhesions, without marked collapse of the lung.

Pathologic Physiology. Acute pleurisy occasions marked local symptoms, beginning with sharp pain on the side affected. This is usually due to the local inflammation and rubbing of the affected parts. There may, however, be extensive neuralgic pains radiating from the center of infection. With the development of effusion, the pain, as a rule, subsides, as does also the irritative cough which attends the first stage, but shortness of breath develops in correspondence with the amount of effusion. Very extensive effusion in the chest may, however, cause even marked pain and tenderness than dry pleural inflammation. The infection in simple pleurisy seems to be a mild one, as fever and constitutional symptoms are rarely marked. Sometimes the temperature is a fluctuating one, and sweating and constitutional depression further suggest suppuration, though the effusion is purely serous. Irregular fever and constitutional symptoms of the kind indicated are habitual in empyema.

INFECTIOUS DISEASES.

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Tuberculosis of the pleura, or tuberculous pleuritis, may be either primary or secondary. Cases of the former are comparatively rare. In most instances the pleural disease is secondary to tuberculosis of the lungs, or to tuberculosis of other adjoining parts. Hematogenic infection may occur under the same conditions as hematogenic infection of the lungs, and frequently the lungs and pleuræ are studded with miliary tubercles at the same time.

When the pleural disease is secondary to tuberculosis of the lungs the appearances vary considerably. In many cases small gray or yellow tubercles are found in the subpleural connective tissue and in the pleura, and the surface may be coated with fibrinous exudate, while the cavity of the pleura may be more or less distended with serofibrinous, hemorrhagic, or purulent liquid. Not rarely the liquid effusions are reabsorbed and dense adhesions are formed, or great thickening of the pleura results. Sometimes considerable calcification of the thickened pleura and of the in

spissated exudate is the terminal result. The tubercle-bacilli are often difficult to demonstrate in the liquid, even by injections into animals, though they may be present in the pleura itself.

Syphilis of the pleura is a doubtful condition. Fresh pleuritis may be found in the neighborhood of a syphilitic gumma; and there are cases of considerable pleural thickening in syphilitic persons in which the disease may possibly be syphilitic, though in these cases, as in similar indurative conditions in the lungs, there is considerable doubt as to the essential nature of the disease.

TUMORS AND PARASITES.

Tumors of the pleura are comparatively rare. Fibromata and lipomata are occasionally seen as small nodular masses in the

FIG. 218.-Endothelioma of pleura: the pleural cavity was distended with effusion, and the lung was compressed and invaded by secondary nodules.

serous or subserous coat of the costal or visceral pleura. Chondromata and even osteomata have been observed. More frequently calcification and ossification of portions of the thickened pleura take place after pleuritis.

Primary sarcoma may spring from the subpleural connective tissue, and, according to Coats, is especially common in children,

and is most frequently of the spindle-cell variety. Primary endothelioma of the pleura has been studied by a number of investiga

In a case under my observation it presented itself as a more or less uniform thickening of the pleura of one side, involving the diaphragmatic reflection in particular. The cavity was filled with hemorrhagic fluid, and there were some nodular enlargements on the surface (Figs. 218 and 219). This is the usual appearance presented. Metastasis may occur in the lung beneath the diseased pleura, or even in more distant parts.

FIG. 219.-Microscopic section from the preceding illustration.

Secondary tumors of the pleura may occur by metastasis or by direct extension. In the former manner sarcomata and carcinomata sometimes involve this structure; by the latter method of involvement mammary tumors and new growths of the mediastinum, the ribs, or other adjacent structures may extend to the pleura.

Parasites.-Echinococcus cysts may originate in the subserous connective tissue of the costal or the visceral pleura, and may rupture into the pleural cavity. Psorospermiæ have been found in pleural effusions. The Amoeba coli has been found in the pus of empyema following hepatic abscess.

CHAPTER V.

DISEASES OF THE GASTRO-INTESTINAL TRACT.

THE MOUTH.

CONGENITAL ABNORMALITIES.

THE most frequent defects in the development of the mouth are cleft palate and harelip. In the former of these the entire hard palate may be divided, generally to one side of the middle line; and there may be associated harelip and fissure of the soft palate. Anteriorly the division occurs between the superior maxillary bone and the intermaxillary bone, the fissure of the lip being also to one side and often extending into the nostril. The soft palate is divided along the middle line, and the uvula may be separated into lateral halves. The lip may be cleft on both sides, so that there is a small central portion connected with the septum of the nose and separated from the lateral portions of the lip. Harelip is more frequently unassociated with cleft palate.

Complete absence of the lips; or unusual shortness, especially of the upper lip; excessive largeness of the mouth by extension of the fissure outward toward the ear; and imperfect development of the lower jaw-bone, are rare congenital conditions.

CIRCULATORY DISTURBANCES.

Anemia of the mucous membranes of the mouth is seen in cases of general anemia, and is often one of the most striking evidences of that condition. It is particularly noticeable in the lips.

Hyperemia. Active hyperemia occurs in the early period of various inflammations, while passive congestion is met with as the result of obstruction of the circulation in pulmonary and cardiac diseases.

Hemorrhages in the form of small petechiæ occur in purpura and other hemorrhagic diseases, and sometimes in infectious fevers.

INFLAMMATION.

Inflammation of the mucous membrane of the mouth is termed stomatitis; inflammation of the tongue is designated by the name glossitis.

Stomatitis may be of varying character and intensity.

Catarrhal stomatitis may result from direct irritation by hot liquids or chemical substances, or may occur in depressed conditions of the general system, possibly as a consequence of infection. It is more common in children than in adults. The mucous