286 HISTOLOGY OF THE MORBID PROCESSES, 



288). In passive hypersemia of the liver the cells situated around the 

 central veins of the lobules suffer atrophy. This is due in part to 

 the pressure exerted upon them, in part to an interruption of the 

 lymphatic circulation, and in part to the fact that the blood reaches 

 them last in its course through the organ and is probably less richly 

 provided with oxygen and other nutritive materials than when it 



FIG. 258. 



Lobule of the liver, showing atrophy from chronic passive congestion. (Kibbert.) In the 

 centre is the central vein, with slightly thickened walls. Surrounding this are the di- 

 lated capillaries, forming the intralobular vessels, between which are the atrophic liver- 

 cells containing pigment. This pigment is probably of biliary origin. The pressure 

 upon the cells must interfere with the discharge of the bile through the bile-capillaries 

 (Figs. 127 and 128), and lead to an accumulation of its constituents within the cells, 

 where the pigment collects. 



passed through the other parts of the vascular system within the 

 liver. The capillaries are enlarged around the central vein ; the 

 hepatic cells between them are diminished in size and pigmented 

 (Fig. 258). 



The growth of tumors may exert a pressure upon neighboring 

 parts, causing their atrophy, the explanation of which is similar to 

 that of atrophy of the liver as the result of passive hypersemia. 

 Pressure upon a tissue does not always, however, occasion atrophy. 

 If the function of a part be to resist pressure, an increase of press- 

 ure may lead to hypertrophy, provided the nutrient supply be 

 sufficient. Thus pressure upon the walls of a bloodvessel may 

 cause them to increase in thickness. 



Aside from the two forms already mentioned, atrophy may be the 

 result of a diminution in the nutritive supply : local, as the result 

 of disease in the vessels of a part ; general, when all the vessels are 



