THE CIRCULATORY SYSTEM. 465 



LYMPHANGIECTASIS. 



Dilatation of the lymph-vessels occurs under a variety of conditions. 

 It may be congenital, or it may be due to some hindrance to the flow of 

 lymph onward as by pressure from any cause, or from the occlusion of 

 the vessels by inflammation. If the dilated vessels form a circumscribed 

 mass, this is often called a lymphangioma (Fig. 181). In certain forms 

 of elephantiasis and in macroglossia the dilatation of the lymph-vessels is 

 an important factor. Its occurrence is not infrequent in the labia, pre- 

 puce, and scrotum. Dilatation of the chyle vessels may occur in the 

 mucous membrane of the intestine and in the mesentery. Filarial lym- 

 phatic varix is of occasional occurrence. ' 



Obstruction of the Thoracic Duct may be due to tumors, 2 or enlarged 

 lymph-nodes, or inflammatory processes in the mediastinum ; to aneur- 

 ism, to thrombosis of the left innominate vein, to insufficiency of the 

 tricuspid valve ; or to inflammatory processes in the wall of the duct. It 

 may occur under various other conditions. It may be compensated by 

 collateral lymphatic anastomoses, or it may lead to various lymphangi- 

 ectasise and to transudation of lymph. Thus chylous ascites may occur. 



Congenital doubling or division and other abnormalities of the tho- 

 racic duct are recorded. 3 



INFLAMMATION. (Lymphangitis.) 



Acute Infective Lymphangitis. Inflammation of the larger lymph-ves- 

 sels is usually secondary and often connected with an infected wound or 

 injury. Owing to the entrance into the lymph trunk of bacteria or other 

 infectious agents, poison of venomous reptiles, insects, etc., the vessels, 

 sometimes for a considerable distance away from the wound, become red, 

 tender, and painful. Under these conditions the appearances which the 

 vessels present vary. In some cases the redness disappears after death 

 and we find no appreciable alteration. In other cases, the walls of 

 the lymph -vessels are more or less densely infiltrated with pus cells, 

 there is proliferation of the eudothelium, and the lumen may contain 

 variable quantities of pus and fibrin and desquamated degenerated en- 

 dothelium. The tissue about the vessels may also be infiltrated with 

 serum and pus. These lesions may undergo resolution and the vessel be 

 restored to its normal condition ; or the vessel wall and surrounding 

 tissue may die or become involved in abscess ; or new connective tissue 

 may form in and about the vessel, sometimes with obliteration of its 

 lumen. The associated lymph -nodes may participate in the inflammatory 

 process. 



1 See Opie, "Filarial Lymphatic Varix," Trans. Assn. Am. Phys., vol. xvi., p 331. 

 ' 2 For bibliography of carcinoma involving the thoracic duct see A. H. Smith, Med. 

 Record, December 2d, 1899, p. 813. 



3 Butler, Jour. Med Res., vol. x., 1903, p. 153 bibliography. 

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