586 THE LIVER. 



cells at the periphery become fatty, so that the nutmeg appearance is still 

 more pronounced. A liver in this condition is usually of medium size, 

 but may be smaller or larger than normal. 



When the congestion is long- continued the veins at the centre of each 

 acinus may become permanently dilated, and the hepatic cells in their 

 meshes become atrophied (Fig. 354), so that the centre of each acinus 

 consists only of dilated capillaries or of these and new connective tissue ; 

 or the dilatation and atrophy of the liver cells may, in circumscribed 

 portions of the organ, involve the entire acinus. In long-continued 

 congestion the liver is usually smaller than normal, and may be slightly 

 roughened or uneven on the surface ; but it is sometimes enlarged. The 

 peculiar nutmeg appearance may be very well marked, or it may not be 

 evident, the organ being of a dark-red color. 



LESIONS OF THE HEPATIC VESSELS. 



THE HEPATIC ARTEEY. 



The hepatic artery is in rare cases the seat of aneurisms which may 

 attain a large size. Such aneurisms may displace the liver tissue, com- 

 press the bile ducts so as to cause jaundice, and may rupture into the 

 stomach or abdomen. 



Owing to its abundant anastomoses, emboli of the branches of the 

 hepatic artery usually induce no marked lesions, but they sometimes 

 result in anaemic and hsemorrhagic infarctions. ' 



THE PORTAL VEIN. 



Thrombosis, Embolism, and Inflammation. Thrombosis of the branches 

 of the portal vein may be produced by weakening of the circulation from 

 general debility marasmatic thrombi; by pressure on the vessel from 

 without, as in cirrhosis, tumors, gall stones, dilatation of the bile ducts, 

 etc. ; by injury; by the presence of foreign materials within the vessel; 

 and as a result of inflammation of its wall, or of embolus. The throm- 

 bus may form in the vessels in the liver or be propagated into them from 

 without. It may partially or entirely occlude them. The clot may be- 

 come organized as a result of endophlebitis, and a permanent occlusion 

 of the vessel ensue. If the clot be a simple, non -irritating one, leading 

 to occlusion, the consequences are usually more marked in the abdomi- 

 nal viscera than in the liver itself. The branches of the hepatic artery 

 form sufficient anastomoses to nourish the liver tissue and prevent its 

 necrosis, even in complete occlusion of the portal vein ; and if occlusion 

 occur slowly the organ may continue to perform its functions. But this 

 obliterative form of thrombosis is usually attended by ascites, enlarge- 

 ment of the spleen, dilatation of the abdominal veins, and sometimes by 

 hsemorrhage from the stomach and intestines. 



1 For a critical summary of recorded cases of anaemic infarcts of the liver see Bald- 

 win, Jour. Med. Research, vol. viii., 1902, p. 431. 



