THE EES2IRATORY SYSTEM. 521 



The Mediastinum. 



INFLAMMATION. Suppurative inflammation may occur either in the anterior or 

 posterior mediastinum. It may be caused by fractures, caries or necrosis of the ster- 

 num and vertebra?, by perforation of the oesophagus, by suppuration of the lymph- 

 nodes, by pleurisy, or may occur without discoverable cause. 



The pus may infiltrate the connective tissue, or may form abscesses which may 

 attain a large size. The inflammation may extend to the pleura or the pericardium, 

 the abscesses may displace the heart, the lungs, or the sternum ; or they may perforate 

 through the skin, into a pleural cavity, the oesophagus, the trachea, or a bronchus. 1 



A few cases of chronic inflammation of the tissues of the mediastinum have been 

 reported chronic mediastinitis. 2 



TUMORS. The most common form of new growth in the mediastinum is that 

 known by the names of lymphoma, lymplw -sarcoma, and lymph-adenoma. 



These tumors are confined to the mediastinum, or they are associated with similar 

 growths in other parts of the body in the disease called "pseudo-leukaemia." Persons 

 between the ages of twenty and thirty years seem to be the most liable to the growth, 

 but it is also not uncommon in children. 



It begins in the lymph nodes in the mediastinum, and at the root of the lung. 

 It increases at first slowly, then more rapidly, and gradually infiltrates the adjoining 

 tissues. In this way the walls of the trachea, bronchi, and aorta, the pericardium, the 

 pleura, and the lung, become infiltrated with compression of the surrounding organs. 



The growth is composed of a fibrous stroma associated with small round cells, the 

 relative quantity of cells and stroma varying in the different cases. 



Besides this form of tumor there may also occur in the mediastinum tumors similai 

 to those which grow in the pleura and behind the peritoneum tumors which resemble 

 both the sarcomata and carcinomata, and which it is difficult to classify. Aberrant 

 thyroid-gland tissue may be found in the mediastinum. 



Complex tumors belonging among the fcetal inclusions or teratomata are of occa- 

 sional occurrence in the anterior mediastinum. 3 They may contain bone, cartilage, con- 

 nective tissue, muscle, hairs, skin, etc. Cysts sometimes lined with ciliated epithelium 

 may form in such tumors. 4 



1 For tuberculous lesions of the tracheo-bronchial lymph-nodes see reference, p. 

 442. 



~ 2 Whipham, Lancet, 1899, vol. i., pp. 882, 947, bibliography. 



3 See Mandlebaum. Am. Jour. Med. Sciences, vol. cxx., p. 64, 19C9. 



4 Consult Hare, "Tumors of the Mediastinum, " Philadelphia, 1889; also Zahn, Vir- 

 chow's Archiv, Bd. cxliii., pp. 170 and 416, 1896; also LohriscTi, Lubarsch and Oster- 

 tag's "Ergebnisse," Jahrg. vii., 1900-1901, p. 912, bibliography. 



