DISEASES OF THE LIVER. 245 



persistent pain in the off-shoulder, ascites, congestion and 

 enlargement of the spleen are among those most commonly 

 met with. 



From a comparative pathological point of view it is most 

 interesting to observe how closely these manifestations of 

 hepatic disorder correspond with those presented by man, 

 in whom the lameness in the right fore-limb is represented 

 by pain in the right shoulder. 



Pain, indeed, may be the primary factor in the produc- 

 tion of this kind of lameness in the horse. 



CONGESTION OF THE LIVER— INTERSTITIAL 

 HEPATITIS. 



Nature and Varieties. — Congestion or engorgement of 

 the liver with blood, or with biliary secretion, is probably 

 the most common of the hepatic diseases of the horse, and 

 is of three varieties, (1) active, (2) passive, and (3) biliary. 



1. Active Congestion. — Activecongestion of the liver always 

 accompanies the process of digestion in health, but it is apt 

 to exceed the normal limits if the food be supplied in ex- 

 cess, or if it be of a too highly stimulating nature. 



2. Passive Congestion. — Passive congestion is the form 

 most commonly met with, and is due to obstruction of the 

 circulation through the hepatic and portal veins. This 

 variety of congestion is more especially associated with ob- 

 struction of the blood-flow, depending on dilatation or 

 valvular disease of the heart, or on disease of the pulmonary 

 organs. 



3. Biliary Congestion. — Biliary congestion, or over-filling 

 of the small bile-ducts with secretion, may arise from active 

 or passive hypersemia, or from both. It is due to obstruc- 

 tion in the ducts from the presence of parasites or other 

 foreign bodies, or to inflammation of the mucous membrane. 

 It usually gives rise to pain, and is sometimes associated 



