466 THE CIRCULATORY SYSTEM. 



Tuberculous Lymphangitis. Tuberculous inflammation occurs both in 

 large and small lymph -vessels. Miliary tubercles and diffuse tubercle 

 tissue may form in the walls and project into the lumen of the larger 

 trunks ; or in the smaller vessels the new growth may entirely fill the 

 lumen, and grow within it, with more or less involvement of the walls. 

 This may occur independently, but it is most frequently seen in connec- 

 tion with tuberculous inflammation of adjacent tissues. Thus from tuber- 

 culous lymph-nodes in the vicinity of the thoracic duct there may be a 

 direct extension of the tuberculous inflammation, an involvement of the 

 walls of the duct, and a growth of tubercle tissue into its lumen. Such 

 growths in the thoracic duct have been shown by Weigert to occur in acute 

 general miliary tuberculosis, and satisfactorily explain the dissemination 

 of the tubercle bacilli. In the vicinity of tuberculous ulcers in the in- 

 testines, furthermore, we often see the subserous lymph-vessels, which 

 pass from the vicinity of the ulcers, distended with the products of tu- 

 berculous inflammation and looking like dense white knobbed cords 

 (Fig. 329). 



Syphilitic Lymphangitis not infrequently occurs in the vicinity of 

 syphilitic ulcers in the primary stage. In later stages there may be 

 thickening of the walls of the vessels and the development of gummy 

 tumors in and about them. 



TUMORS. 



The relation of the endothelium of the lymph-vessels and spaces to 

 endotheliomata has been already mentioned in the section on Tumors. 



The dissemination of malignant tumors through the lymph channels 

 is of frequent occurrence, and is particularly marked in the case of car- 

 cinoma. In the vicinity of carcinomata the lymph-vessels are not infre- 

 quently crowded with the tumor cells, forming white, irregular cords ; 

 or small masses of the tumor cells may be found in the lymph- vessels, 

 either near to or remote from the tumor. White, irregular networks are 

 often formed in this way beneath the pleura in carcinoma of the lung 

 (Fig. 300), or beneath the capsule of the liver. Transverse sections of 

 lymph-vessels thus distended show sometimes swelling and detachment 

 of the endothelium and a crowding of the lumen with tumor cells. 



